* style(app): theme native scrollbars in tool call detail views
Apply CSS scrollbar-color to all ScrollViews in ToolCallDetailsContent
and DiffViewer so the browser scrollbar matches the app's dark theme
instead of showing the default white native scrollbar.
* refactor: split useWebScrollbarStyle into .web.ts/.native.ts platform files
- Native shim returns undefined without calling useUnistyles
- Web variant uses properly typed WebScrollbarStyle interface instead of `as any`
- Add .d.ts for TypeScript module resolution
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Co-authored-by: Mohamed Boudra <boudra.moha@gmail.com>
Use Metro .web.tsx resolution to separate native gesture arbitration
(RNGH ScrollView, waitFor, closeGestureRef) from web (plain RN ScrollView),
fixing text selection drag on desktop web.
