feat: add responsive ultrawide work lanes

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.