Optimize expanded image preview rerenders

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What Changed

• Removed the ExpandedImageDialog prop-mirroring Effect that copied preview into local state.
• Split the dialog into a keyed outer reset boundary and an inner component that owns only local image navigation offset state.
• Moved the necessary keydown browser subscription into a named useExpandedImageKeyboardShortcuts hook using useEffectEvent.

Why

React Doctor flagged the old implementation as mirrored prop state via Effect. That caused an extra stale render whenever the parent selected a different preview. Keying the inner dialog resets navigation state from the selected preview without an Effect, while keeping arrow-key navigation local to the dialog.

UI Changes

React Scan recordings are included in this PR:

• Before: docs/perf/expanded-image-dialog-react-scan-before.webm
• After: docs/perf/expanded-image-dialog-react-scan-after.webm

The same interaction, two parent preview switches, went from 5 total dialog subtree commits before to 3 total commits after. Metadata is in:

• docs/perf/expanded-image-dialog-react-scan-before.json
• docs/perf/expanded-image-dialog-react-scan-after.json

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

Verification:

• npx -y react-doctor@latest . --project @t3tools/web --diff main --verbose
• bun fmt
• bun lint
• bun typecheck

  

Note

Reduce rerenders in ExpandedImageDialog by keying content on preview state

• Replaces the memoized ExpandedImageDialog with a thin wrapper that renders a keyed ExpandedImageDialogContent child, forcing a remount when preview.index, image count, or image sources change via a new getPreviewResetKey helper.
• Simplifies internal navigation state from a cloned preview object to a single indexOffset integer, deriving currentIndex as (preview.index + indexOffset) % images.length.
• Extracts keyboard handling into a useExpandedImageKeyboardShortcuts hook using useEffectEvent for a stable listener.
• Behavioral Change: the content component now remounts on preview changes rather than re-rendering in place, and React.memo/useCallback are removed.

^{Macroscope summarized 64fcb1a.}