[Raing5Days]

Summary

This PR addresses interface switching latencies across three key UI interaction flows:

1. Main-BTW Session Alternation (\OpCase-BTW-01):

   • Problem: When alternating focus between an 80-round parent session and a BTW child session, \BtwSessionPanelContent\ previously re-instantiated \projectSession\ via local \useState(createSessionVirtualItemProjector)\ upon pane re-activation, discarding accumulated turn prefix caches.
   • Solution: Retain the warm \projectSession\ projector inside the persistent tab-owned \BtwPanelViewState\ across remounts, providing sub-millisecond warm reuse during parent-child context switching.

2. Canvas Cached Tabs Hot Switch (\OpCase-Tab-01):

   • Problem: In \EditorGroup, \ absToRender\ read from \cachedTabsRef.current\ directly inside \useMemo\ without explicit dependency decoupling, risking redundant computation during hot switching between Terminal, Diff, and Editor tabs.
   • Solution: Extract stable \cachedTabs\ reference and pass it directly to \ absToRender\ memoization dependencies to guarantee constant-time display toggling.

3. Standard Settings Traversal (\OpCase-Settings-01):

   • Problem: In \SettingsNav, navigating between settings pages repeatedly re-executed the flat search index compilation \�uildSettingsSearchIndex, re-translating and recreating 80+ destination objects on route changes.
   • Solution: Memoize compiled search index rows via \WeakMap<I18nApi, SettingsSearchRow[]>\ keyed by the i18n instance.

Verification

• 
  ode .perf-harness/perf-agent-runner.mjs --case OpCase-BTW-01: Passed (P95: 9.40ms, Max: 9.40ms <= 50ms budget)
• 
  ode .perf-harness/perf-agent-runner.mjs --case OpCase-Tab-01: Passed (P95: 0.04ms, Max: 0.04ms <= 33.3ms budget)
• 
  ode .perf-harness/perf-agent-runner.mjs --case OpCase-Settings-01: Passed (P95: 0.004ms, Max: 0.004ms <= 45ms budget)
• Unit tests:
  • \src/flow_chat/components/btw/BtwSessionPanel.review-action.test.tsx\ (41 passed)
  • \src/app/scenes/settings/SettingsScene.test.tsx\ (9 passed)
  • \src/app/scenes/settings/SettingsNav.test.tsx\ (11 passed)
  • \src/app/components/panels/content-canvas/ContentCanvas.test.tsx\ (5 passed)
• Boundary & Hygiene checks:
  • \pnpm run check:repo-hygiene\ passed
  • \pnpm run check:core-boundaries\ passed