feat: add interactive VT and workspace command plane

docs/UX_VERTICAL_SLICE.md

@@ -67,11 +67,18 @@ surface rather than a hosted Lumbridge control plane.
    in a stable order.
 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,
+   Context, Goal, and Review. Switching surfaces keeps one pane identity.
+8. A compact decision shelf may show local-analyst choices below the work
+   surface. It labels its model/provider, trace scope, and whether suggestions
+   are inert; no choice is visually conflated with an approved action.
 
 ## Keyboard task flow
 
-- Arrow keys or `h/j/k/l`: move focus through the 2×3 pane grid.
-- `1` through `6`: focus a pane directly.
+- `Alt+Arrow` or `Alt+h/j/k/l`: move focus through the 2×3 pane grid while
+  leaving ordinary terminal arrows and text available to the PTY.
+- `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.
 - Typing while the palette is open changes its query; arrows change the result;
   `Enter` runs it; `Escape` closes it and restores pane focus.