fix: solve #3490 — cannot re-enable Show Preset Bar after toggling off

[github-actions]

Summary

• Root cause: The "Show Preset Bar" toggle is only accessible from within the PresetsBar's cog icon dropdown and a secondary toggle in the AddTabButton ("+" button) dropdown. When the user hides the preset bar, the primary toggle disappears with it. The secondary toggle in the "+" dropdown exists but is not discoverable — users cannot find a way to re-enable the bar.
• Fix: Added a "Show Preset Bar" switch to the General settings page (Settings > General), following the same pattern as the existing "Resource monitor" toggle. This provides a reliable, always-accessible location to re-enable the preset bar.
• The fix uses the existing getShowPresetsBar/setShowPresetsBar tRPC procedures with optimistic updates and rollback, matching the pattern of all other toggles on that page.

What changed

File	Change
settings-search.ts	Added BEHAVIOR_SHOW_PRESETS_BAR setting ID and searchable entry with keywords (preset, bar, show, hide, toggle, etc.)
BehaviorSettings.tsx	Added "Show Preset Bar" switch toggle with tRPC query/mutation and optimistic updates
settings-search.test.ts	Added 3 tests verifying the setting is searchable and in the correct section

Test plan

• bun test on settings-search.test.ts — all 10 tests pass (3 new + 7 existing)
• bun run lint:fix passes cleanly
• Manual: Open Settings > General — verify "Show Preset Bar" toggle appears
• Manual: Toggle preset bar off from cog icon, then re-enable from Settings > General
• Manual: Search "preset bar" in settings search — verify the toggle is found

Closes #3490

---

Summary by cubic

Adds a “Show Preset Bar” toggle to Settings > General so users can re-enable the preset bar after hiding it. Fixes the lockout caused when the primary toggle disappears with the bar (closes #3490).

• Bug Fixes
  • Added “Show Preset Bar” switch in Behavior settings using existing getShowPresetsBar/setShowPresetsBar with optimistic updates and rollback.
  • Indexed the setting in settings search with helpful keywords; added tests to verify search results and section placement.

^{Written for commit b2d3072. Summary will update on new commits.}