Stabilize root app shell renders

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What Changed

• Hoisted the static root app shell JSX out of RootRouteView so route-level re-renders do not recreate the CommandPalette / AppSidebarLayout element tree.
• Moved the browser chrome theme synchronization effect into a named hook, useBrowserChromeThemeSync.
• Added React Scan before/after recordings:
  • Before recording
  • After recording

Why

react-doctor flagged static JSX in src/routes/__root.tsx as a performance warning because the root shell was recreated on every root route render. Hoisting the shell makes the shared shell element stable while the nested Outlet continues to update from router context.

Scan results:

• Before: react-doctor score 73, 253 warnings.
• After: react-doctor score 74, 252 warnings.
• The rendering-hoist-jsx warning for src/routes/__root.tsx is removed.

UI Changes

No intended visual changes. React Scan recordings above capture the same route-navigation flow with React Scan enabled before and after the fix.

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:

• bun fmt
• bun lint
• bun typecheck

  

Note

Stabilize root app shell renders by hoisting JSX to a module-level constant

• Extracts the CommandPalette -> AppSidebarLayout -> Outlet JSX tree into a module-level APP_SHELL constant in __root.tsx, replacing a per-render local variable to prevent unnecessary re-renders.
• Extracts the browser chrome theme sync logic into a new useBrowserChromeThemeSync(pathname) hook, replacing an inline useEffect in RootRouteView.

^{Macroscope summarized 993571a.}