feat: add responsive ultrawide work lanes

docs/ARCHITECTURE.md

@@ -71,21 +71,23 @@ shutdown against ordered raw-byte output. The GPUI slice feeds one actor session
 through the terminal engine while five surfaces retain deterministic comparison
 output. Its adapter groups adjacent cells into native GPUI paint runs and renders
 ANSI/indexed/RGB colors, emphasis, hyperlinks, and cursor shapes. Window geometry
-drives terminal rows and columns and resizes both the engine and PTY. Selection,
-scrollback navigation, mouse reporting, and a lower-level terminal canvas remain.
-This actor still runs in-process; moving the same framework-neutral
-contract behind local authenticated IPC is the next durability step. See
-decisions 0004 and 0005.
+drives terminal rows and columns and resizes both the engine and PTY. The engine
+now exposes retained-history offsets and page/top/bottom viewport movement
+without writing scroll keys to the PTY. Text selection, mouse reporting, and a
+lower-level terminal canvas remain. This actor still runs in-process; moving the
+same framework-neutral contract behind local authenticated IPC is the next
+durability step. See decisions 0004 and 0005.
 
 ## Default workspace composition
 
-The default desktop workspace is a vertical 3×1 composition: the top 20% holds
-pane, agent, tool, context, and goal state; the middle 60% is the active terminal
-or work surface; the bottom 20% is the answer, choice, chat, and approval shelf.
-Six deterministic surfaces still update in the spike so performance comparisons
-remain meaningful, but only the selected surface owns the large work region.
-Users may deliberately split that region later; a dashboard grid is not the
-calm default. See decision 0008.
+The default desktop workspace has three horizontal bands: the top 20% holds pane,
+agent, tool, context, and goal state; the middle 60% holds responsive vertical
+work lanes; and the bottom 20% is the answer, choice, chat, and approval shelf.
+The work region shows one lane in compact windows, three at normal desktop
+widths, and five on a 3440 px ultrawide. The selected lane alone owns keyboard
+input. Six surfaces continue updating so performance comparisons remain
+meaningful, with a sliding visible window keeping the selected pane onscreen.
+See decisions 0008 and 0009.
 
 We should evaluate, not blindly copy, WezTerm, Zellij, RMUX, tmux, and cmux. The
 first spike must compare a reusable terminal crate with a small first-party layer.

docs/PRODUCT_SPEC.md

@@ -66,11 +66,13 @@ surface change never silently launches a process, moves the pane to another
 host, or changes which agent owns the session. Unsupported surfaces are shown as
 unavailable rather than simulated.
 
-The default workspace is a 3×1 vertical composition: the top 20% shows context,
-pane/agent state, tools, and goal; the middle 60% is the selected terminal or
-work surface; the bottom 20% is the decision shelf. Multiple panes may continue
-working offscreen and remain one shortcut away. Explicit split and dashboard
-layouts remain supported, but they do not displace the primary-terminal default.
+The default workspace has three horizontal bands: the top 20% shows context,
+pane/agent state, tools, and goal; the middle 60% is a responsive set of vertical
+work lanes; and the bottom 20% is the decision shelf. The work band shows one
+lane in compact windows, three at normal desktop widths, and up to five on an
+ultrawide display. One lane owns keyboard input at a time, and selecting a lane
+never pauses the others. Explicit split trees and dashboard layouts remain
+supported, but they do not displace this terminal-first default.
 
 An optional decision shelf sits below the active work surface. It may show an
 answer draft, two or three concrete choices, why each was suggested, and the

docs/TESTING.md

@@ -118,10 +118,14 @@ who already have the final cargo-watch release installed.
   blocked OSC 52 behavior, key encoding, application-cursor mode, and resize.
 - `lumbridge-core` tests capability-gated split/select/rename/close commands,
   idempotent request IDs, close-tree promotion, and atomic agentic setup plans.
-- The GPUI slice tests its key-event adapter, 20/60/20 geometry-to-PTY sizing,
-  xterm 256-color conversion, styled-run coalescing, and cursor-run boundaries.
-  It renders one real actor-owned VT session while five surfaces continue their
-  deterministic background workload.
+- The GPUI slice tests its key-event adapter, responsive one/three/five-lane
+  geometry, selected-pane lane windowing, 20/60/20 geometry-to-PTY sizing, xterm
+  256-color conversion, styled-run coalescing, cursor-run boundaries, and
+  scrollback shortcut routing. It renders one real actor-owned VT session while
+  five surfaces continue their deterministic background workload.
+- `lumbridge-terminal` retains 10,000 history lines by default and tests
+  framework-neutral page/top/bottom viewport movement, revision changes, and
+  live-bottom no-ops without sending history-navigation bytes to the child PTY.
 - The current-GPUI probe compile-checks real AccessKit element wiring and real
   platform input-handler installation. Unit tests cover its semantic tree and
   UTF-16/UTF-8 composed-text mutations. OS screen readers, IME candidate windows,

docs/UI_SPIKE_SCORECARD.md

@@ -24,9 +24,9 @@ from macOS and Linux and the hard gates pass.
 The current programs establish dependency, build, launch, and interaction
 baselines. GPUI now routes a real PTY through a VT engine and keyboard encoder,
 paints coalesced styled cell runs and cursor shapes, and derives PTY rows/columns
-from its 60% terminal band when the window changes. Selection, scrollback
-navigation, mouse modes, a native Markdown editor, and one isolated browser child
-remain.
+from its responsive one/three/five-lane 60% terminal band when the window
+changes. Retained-history page/top/bottom navigation is wired. Text selection,
+mouse modes, a native Markdown editor, and one isolated browser child remain.
 
 ## Ubuntu baseline — metal, 2026-08-31
 
@@ -87,9 +87,9 @@ fallback.
 ## Measurement semantics
 
 Both renderers retain the same all-deterministic six-surface action stream for
-comparison. GPUI now presents the selected surface in a 20/60/20 vertical
-workspace while one terminal fixture is replaced with a real actor-owned VT
-session and five deterministic surfaces keep running offscreen. Counters
+comparison. GPUI now presents a 20/60/20 workspace whose middle band shows one,
+three, or five vertical work lanes while one terminal fixture is replaced with a
+real actor-owned VT session and five deterministic surfaces keep running. Counters
 separate external PTY batches/lines from total model updates. The GPUI footer
 reports dispatch-to-element-build p50/p95 over a bounded 256-sample window. It
 is deliberately not called key-to-present or frame-present latency: neither

docs/UX_VERTICAL_SLICE.md

@@ -10,12 +10,14 @@ framework decision gate, not a decorative dashboard.
 ## Current-run audit
 
 The first 2026-08-31 GPUI baseline proved six-surface density but gave every
-pane equal visual priority. The current slice replaces that dashboard with a
-3×1 default: 20% context and pane selection, 60% active work surface, and 20%
-decision shelf. Keyboard focus, command-palette input, live PTY input, styled VT
-cells, cursor shapes, and geometry-driven resize are wired. Remaining visible
-gaps are terminal selection/scrollback, real decision-shelf actions, usage-detail
-provenance, and end-to-end platform accessibility/IME.
+pane equal visual priority. The current slice replaces that dashboard with three
+horizontal bands: 20% context and pane selection, a 60% responsive work region,
+and a 20% decision shelf. The work region shows one, three, or five vertical
+lanes according to available width. Keyboard focus, command-palette input, live
+PTY input, styled VT cells, cursor shapes, geometry-driven resize, and retained-
+history navigation are wired. Remaining visible gaps are terminal text selection
+and mouse modes, real decision-shelf actions, usage-detail provenance, and end-to-
+end platform accessibility/IME.
 
 Screenshots for the audit are stored outside Git under
 `~/shots/2026-08/lumbridge-ui-audit/`. Accessibility and IME correctness cannot
@@ -40,8 +42,8 @@ research, not source assets for Lumbridge. We adapt these interaction patterns:
   cards;
 - a quiet top tab strip for mixed terminal, Markdown, browser, and review
   surfaces;
-- one primary work surface with optional splits, instead of forcing every
-  surface into an equal dashboard tile;
+- a primary work region with a small responsive number of equal vertical lanes,
+  instead of either one ultrawide terminal or a dense equal-card dashboard;
 - narrow contextual tools, such as files, review, or Buzz, that can collapse
   when the terminal needs the space;
 - usage and agent state at the edge of the workspace rather than in modal
@@ -62,8 +64,9 @@ surface rather than a hosted Lumbridge control plane.
    the selected pane receives the accent treatment.
 4. A waiting pane uses an amber semantic label in both the context band and
    attention sidebar. The label always includes words such as `NEEDS INPUT`.
-5. The middle 60% gives the selected terminal or work surface uninterrupted
-   reading space and retains target, harness state, dimensions, and surface tabs.
+5. The middle 60% gives one, three, or five terminal/work lanes uninterrupted
+   height and retains target, harness state, dimensions, and surface tabs. The
+   selected lane alone owns keyboard input.
 6. The footer groups connection state, selected-harness identity, usage-window
    provenance, and burn forecast into readable regions.
 7. The selected pane has a quiet surface strip for Terminal, Browser, Tools,
@@ -79,6 +82,8 @@ surface rather than a hosted Lumbridge control plane.
 - `Alt+1` through `Alt+6`: focus a pane directly while leaving terminal digits
   available to the PTY.
 - `Cmd+K` on macOS or `Ctrl+K` on Linux: open the command palette.
+- `Shift+PageUp/PageDown`: move the selected live terminal through retained
+  history; `Shift+Home/End` jumps to the history top/live bottom.
 - Typing while the palette is open changes its query; arrows change the result;
   `Enter` runs it; `Escape` closes it and restores pane focus.
 - `Enter` on a waiting agent opens its request detail. Approval remains a
@@ -92,8 +97,9 @@ receive the same state transitions and tests.
 
 - In the first actor integration, one terminal pane consumes ordered output from
   a real local PTY while each deterministic tick updates the other five
-  surfaces offscreen. The all-deterministic constructor remains available for
-  framework comparison and replay tests.
+  surfaces. One, three, or five are visible according to available width; the
+  all-deterministic constructor remains available for framework comparison and
+  replay tests.
 - One pane enters and leaves `needs input` through a deterministic event.
 - Markdown, browser-boundary, and review panes update counters without using a
   web application shell.

docs/decisions/0008-primary-terminal-3x1-workspace.md

@@ -2,22 +2,21 @@
 
 Status: accepted for the native vertical slice.
 
-Lumbridge defaults to three vertical bands in one column. The top 20% exposes
+Lumbridge defaults to three horizontal bands in one column. The top 20% exposes
 pane, agent, tools, context, goal, target, and attention state. The middle 60%
-belongs to the active terminal or work surface. The bottom 20% holds answers,
-choices, chat, approvals, and the local-analyst boundary.
+is the terminal-first work region. The bottom 20% holds answers, choices, chat,
+approvals, and the local-analyst boundary.
 
-This composition favors the surface where engineers type and read for most of
-the day. It keeps context and decisions visible without making six equally sized
-cards compete for attention. Pane selectors and keyboard shortcuts switch the
-large work surface. Users may later create deliberate splits or dashboard grids,
-but those are workspace choices rather than the default visual hierarchy.
+This composition favors the region where engineers type and read for most of the
+day. It keeps context and decisions visible without making every surface a small
+dashboard card. The middle region may contain a responsive number of vertical
+work lanes under decision 0009; the selected lane alone owns keyboard input.
 
 The framework spike retains six updating surfaces even when five are offscreen.
 That preserves the earlier streaming and reducer workload for performance
 comparison. Hidden surfaces do not receive keyboard input merely because they
 continue to update.
 
-Window geometry determines the middle band's terminal rows and columns. The UI
+Window and lane geometry determine each terminal's rows and columns. The UI
 resizes the terminal engine and PTY through the bounded runtime actor; it does
 not resize only the text view or infer terminal wrapping after the fact.

docs/decisions/0009-responsive-ultrawide-work-lanes.md

@@ -0,0 +1,24 @@
+# 0009: The primary work region uses responsive vertical lanes
+
+Status: accepted for the native vertical slice.
+
+The middle 60% work region shows one vertical lane in compact windows, three at
+normal desktop widths, and five when at least 2800 px remains after the sidebar.
+A 3440 px ultrawide therefore presents five lanes. A sliding window over the six
+comparison panes always keeps the selected pane visible.
+
+This is not a return to the original 2×3 dashboard. Every lane receives the full
+work-region height, the surrounding context and decision bands remain stable,
+and only the selected lane owns keyboard input. Clicking a lane selects it. Pane
+processes and output continue independently of selection.
+
+Terminal geometry is computed from the actual width of one lane, including gaps
+and insets. The selected real PTY is resized through the runtime actor when the
+responsive lane count or window bounds change. On the 3440×1440 reference
+display the current fixed-cell spike derives approximately 71 columns by 40
+rows per lane.
+
+The first actor slice still owns one real PTY and five deterministic comparison
+surfaces. Promoting the runtime boundary from one actor to a pane-indexed session
+registry is required before all five visible terminal lanes can own independent
+real processes.