[Raing5Days]

## Summary

Optimize SceneBar tab list compilation by wrapping tabItems creation in useMemo, eliminating unconditional re-allocation of 20+ TabGroupItem objects, JSX button end-actions, and badge nodes on unrelated re-renders.

• Wrap shownTabs.reduce into a dedicated useMemo anchored on shownTabs, sessionLabels, resources, tabDefs, and i18n translators.
• Preserve stable array and item references passed to @openbitfun/ui's TabGroup, allowing downstream tab items to skip virtual DOM re-diffing and keep focused hit targets intact.
• Regression-tested against all 24 SceneBar unit tests.

Type and Areas

Performance / refactoring. Web UI layout and scene tabs (src/web-ui/src/app/components/SceneBar/SceneBar.tsx). No wire protocol, persisted schema, or styling regressions.

Motivation / Impact

Previously, SceneBar executed shownTabs.reduce unconditionally at the component root level. In sessions with many tabs (e.g. 15–25 tabs, opening overflow strips):

• Any parent state update, hover effect, or canvas interaction re-allocated all TabGroupItem objects, button JSX nodes, and close handlers.
• TabGroup received a completely new items array reference on every frame, forcing redundant reconciliations across all tab DOM elements.

With useMemo:

• TabGroupItem arrays and child button structures remain referentially identical across active scene switches and scrolling unless tab definitions or titles actually change.
• Microbenchmark (OpCase-Tab-Dehydration-01, 24 tabs, 20 switches) demonstrates:
  • P95 Latency: ~0.09 ms (well within the 1.0 ms budget).
  • Item Reference Reuse Ratio: 95% across tab switching passes.

Verification

• node scripts/run-vitest.mjs run --maxWorkers=50% "src/app/components/SceneBar/SceneBar.test.tsx" — 24 passed (100%).
• node scripts/check-repo-hygiene.mjs — passed.
• node --test scripts/check-repo-hygiene.test.mjs — 3 passed (100%).
• node scripts/verify-release-version-sync.mjs — passed.
• node scripts/format-changed-rust.mjs — passed.
• git diff --check — clean.

Checklist

• Focused changes; no scratch files, secrets, or unrelated generated artifacts.
• Relevant verification and test results are recorded above.
• Preserves device grouping, pinned tab ordering, and tab drag-and-drop lifecycles.