feat(ui): implement command palette (Component 34) with tests
- commandpalette.js: CommandPaletteManager with fuzzy scorer, time parsing,
command registry (20 commands), recent history, entity search, mode gating
- commandpalette.css: modal overlay, search input, result list styles
- commandpalette.test.js: 64 tests covering fuzzy match, time parsing, commands
completeness, keyboard nav, recent history, expert-mode gating, positioning
- app.js: spaxelGetState() exposure and Ctrl+K fallback listener
- index.html: includes commandpalette.css and commandpalette.js
- explainability.js + explain.go: detection explainability backend/frontend
- hub.go + server.go: dashboard WebSocket and API updates
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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