Optimize settings sidebar nav rerenders

[cursor]

What Changed

• Split settings sidebar nav item metadata into a non-component module.
• Extracted each settings sidebar row into a memoized SettingsSidebarNavItem component with a stable selection callback.
• Added React Scan before/after recordings and render-count artifacts:
  • docs/react-scan/settings-sidebar-nav/before.webm
  • docs/react-scan/settings-sidebar-nav/after.webm
  • docs/react-scan/settings-sidebar-nav/before-counts.json
  • docs/react-scan/settings-sidebar-nav/after-counts.json

Why

React Doctor plus a manual React Scan pass showed the Settings navigation rerendering every sidebar menu row during settings route changes. For the same interaction path (Settings -> Keybindings -> Providers -> Source Control -> General), React Scan render logs changed from:

• SidebarMenuItem: 37 before -> 16 after
• SidebarMenuButton: 37 before -> 16 after

Unaffected settings rows now remain memoized while the active row changes.

UI Changes

Interaction recordings with React Scan enabled are committed in:

• Before: docs/react-scan/settings-sidebar-nav/before.webm
• After: docs/react-scan/settings-sidebar-nav/after.webm

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for any UI changes
• I included a video for animation/interaction changes

Validation:

• react-doctor scan after fix: no SettingsSidebarNav diagnostics
• bun fmt
• bun lint
• bun typecheck

  

Note

Reduce rerenders in settings sidebar nav by extracting SettingsSidebarNavItem

• Extracts nav item data (types, constants) into SettingsSidebarNav.items.ts to keep it stable across renders.
• Adds a memoized SettingsSidebarNavItem component that uses useCallback for its select handler, preventing unnecessary child rerenders.
• Behavioral Change: the Back button padding changes from px-2 py-2 to p-2, which is visually equivalent but uses a different Tailwind class.

^{Macroscope summarized 654f876.}