Polish command palette search and hierarchy

[brsbl]

Human comments

What was wrong

Command search and thread search used competing presentations, the results viewport and footer did not read as one stable keyboard surface, and thread-result metadata competed with titles. The older palette implementation also needed to retain Settings and plugin-page destinations now present on main.

What changed

• Move thread search into an explicit nested command-palette mode with Backspace/Escape navigation.
• Keep the keyboard footer visible, use shared keycap/control tokens, and clip/fade the scrolling results at the footer boundary.
• Group resting commands, distinguish drill-in commands, and hide an empty Plugins group.
• Refine search-field, tab, filter, metadata, state-label, theme, highlighting, and thread-result hierarchy using existing tokens.
• Preserve Settings, plugin settings, plugin pages, plugin command actions, split opening, keyboard navigation, and search ranking.
• Keep draft search on the existing single new-thread draft contract so this layer does not depend on the experimental sidebar draft-slot system.
• Add focused coverage for root and nested modes, footer behavior, scrolling, highlighting, thread states and filters, themes, and preserved destinations.

No public or wire contracts changed.

Screenshots

Both captures use the same dev data, nested Search threads flow, route, light theme, and 1440×900 viewport.

Before — parent head 64529ff20: the nested thread-search palette has the older search/result treatment and no persistent footer

After — PR head d136783a6: the Threads tab, quieter metadata, state filter, and persistent keyboard footer form one surface

How you verified

• git diff --check
• Remote CI passed for the final head, including checks, app/server/package tests, integration tests, and Linux/macOS package smoke.
• The exact final-head branch app launched successfully with the repository standard launcher on Node 22.
• Drove the exact parent and PR-head branch apps over CDP in Chrome for Testing 151.0.7922.71 using the same fixture and viewport.
• Entered nested Search threads from Command-K and confirmed the refined search/result hierarchy plus the always-visible keyboard footer.
• Per repository policy, no CI-equivalent tests, typechecks, lint, or builds were run locally.

Fixes #

BB-Thread-ID: thr_ccffp4w2p2

AGENT GENERATED

[brsbl]

Superseded by the focused command-palette stack: #2873 owns nested thread search and result execution, #2877 owns persistent keyboard guidance and viewport clipping, and #2878 owns thread-search control and metadata hierarchy.