feat(ui): W leader chords and palette commands for tabs and panes (RIG-4445)

[rigel-mintaka]

This PR is part of a stack containing 7 PRs:

1. main
2. refactor(ui): extract parseRoute and add ViewScope with useView (RIG-4439) #1652
3. refactor(ui): move routed surfaces and agent-workspace state onto the view scope (RIG-4442) #1675
4. feat(ui): window layout model, hash sync and session persistence (RIG-4443) #1743
5. feat(ui): view tab strip with keep-alive and open-in-tab links (RIG-4444) #1755
6. "feat(ui): W leader chords and palette commands for tabs and panes (RIG-4445)" (this PR)
7. feat(ui): two-pane split with a resizable splitter (RIG-4446) #1780
8. fix(ui): chrome cleanup: drop ADE and usage bar, Session Log naming, pane edges, row re-measure (RIG-4771) #1811

Tabs T5 of docs/designs/ui/compass-in-window-tabs/design.md §T5 (RIG-4445), stacked on T4 #1755. It adds the §A6 W leader chords (OQ-1: leader W in both hosts, focus-gated like G).

• keyboard/keymap.ts: the §A6 table rows, exactly as listed:
  • W N new tab, W X close
  • W ] and W [ next and previous
  • W 1–W 9 go to tab N
  • W V and W S split right and down
  • W O closes the other pane
  • W H and W L focus the first and second pane
• tab.moveLeft and tab.moveRight have no chord, because §A6 lists none; they are palette commands only.
• keyboard/spine.ts: registers the commands below against dispatchLayout.
  • Tab commands: tab.new, tab.close, tab.next, tab.prev, tab.goto.1–tab.goto.9, tab.moveLeft, tab.moveRight.
  • Pane commands: pane.splitRight, pane.splitDown, pane.closeOther, pane.focusFirst, pane.focusSecond.
• store.ts: passes the layout accessor and dispatchLayout to the spine. Two shared paths serve both the strip and the commands:
  • closeTab keeps focus on the new active tab button when the closed tab's button had focus.
  • focusPane moves DOM focus into the target pane when focus is outside both panes.
• App.tsx: focus moving into a pane makes that pane the focused one, so layout focus follows DOM focus. view-panel.ts holds the panel ids and panel focus helper that App and the store share.
• Palette entries come from the registry, with titles per §A3/§A6 ("New tab", "Close tab", "Move tab left", "Go to tab N", …).

Readings:

• W N opens /, using the §A3 open dedupe: on a tab already showing Bridge, it focuses that tab. RIG-4676 asks Matt whether "New tab" should always open a new tab.
• Next and previous wrap, matching the tab strip's arrow keys.
• Go-to and move ignore out-of-range targets.
• Pane commands on a single-view tab are no-ops in the reducer. Until T6 (RIG-4446) adds the splitter, a split tab renders its two panes stacked, so "Split right" and "Split down" look the same.

Tests

• New and extended tests:
  • keymap.test.ts: the full W chord-to-command map. The existing authoring-invariant test covers the new rows.
  • spine.test.ts and tab-keep-alive.test.tsx: outcomes on a real store, not emitted actions. Covered: New tab from Bridge and from a topic tab, New tab at the tab cap (notice), closing the last tab (goes to /), wrap, go-to past the end, move bounds, split and close-other, and pane focus moving DOM focus both ways.
  • dispatch.test.ts: w n runs tab.new on a non-editable target and runs nothing in a focused composer.
  • TabStrip.test.tsx: Close tab from a focused tab button, and from the palette, leaves focus on the new active tab.
  • Palette.test.tsx: lists every command.
• ShortcutsOverlay.test.tsx: the "Bridge" filter now expects 3 rows, because tab.new carries a bridge keyword.
• e2e tab-strip.spec.ts: W N opens a tab and W X closes it, and composer text is untouched.
• moon run compass-ui:test: 1285 pass, 0 fail. Typecheck, stylelint and biome are clean.
• Playwright visual-smoke + dev-boot + tab-strip: 16 passed, with no baseline change.

Spec-impact: none.
Ledger-impact: none

Co-authored-by: Matt Wilkinson matt@rigel.build

[linear-code]

RIG-4445

[github-actions]

Compass engineering docs preview: https://compass-ui-rig-4445-tab-chor.compass-eng-docs.pages.dev

Deployed from compass-ui/rig-4445-tab-chords at d7a5fe9.

[trunk-io]

This pull request is queued for merge as part of 1798, which will merge 1652, 1675, 1743, 1755, 1770, 1780, 1787, 1798.

[trunk-io]

This pull request was merged into main as part of stacked PR 1798.