Avoid effect-driven PR dialog resets

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What Changed

• Split PullRequestThreadDialog into a keyed outer wrapper plus inner content so initialReference/open changes reset local dialog state through component ownership instead of a synchronous setState effect.
• Moved the remaining DOM focus/select synchronization into a named hook (useFocusReferenceInputWhenOpen).

Why

React Doctor flagged the dialog reset effect as set-state-in-effect, prop-state synchronization, cascading state updates, derived state, and reset-all-state-on-prop-change. Keying the inner dialog content follows React's guidance for resetting state on prop changes and avoids the stale intermediate render caused by resetting state after commit.

React Doctor after scan: web report improved from 133 errors / 1066 warnings / 1199 total diagnostics to 130 errors / 1063 warnings / 1193 total diagnostics. The dialog reset diagnostics are gone; remaining dialog findings are pre-existing compiler/manual memoization warnings outside this reset path.

UI Changes

No user-facing UI design change. Interaction behavior was verified with React Scan enabled:

• Before recording: react_scan_pr_dialog_before_v2.mp4
• After recording: react_scan_pr_dialog_after_v2.mp4

Both recordings use the same temporary diagnostics surface to swap initialReference 123 -> 456 -> 123 while the real dialog remains open. React Scan purple render highlights are visible during the swaps.

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:

• bunx --bun react-doctor@latest apps/web --offline --fail-on none --json
• vp check (run with Node 24.16.0 on PATH)
• vp run typecheck (run with Node 24.16.0 on PATH)

  

Note

Avoid effect-driven state resets in PullRequestThreadDialog by using key-based remounting

• Splits PullRequestThreadDialog into a thin wrapper and a new PullRequestThreadDialogContent child in PullRequestThreadDialog.tsx
• The wrapper computes a stateResetKey from open and initialReference and passes it as key to the content component, so React remounts the child instead of running a manual state-reset useEffect
• Extracts focus/select logic into a new useFocusReferenceInputWhenOpen hook that uses requestAnimationFrame instead of a raw effect

^{Macroscope summarized 7544d1c.}

[github-actions]

🚀 Expo continuous deployment is ready!

• Project → t3-code
• Platforms → android, ios
• Scheme → t3code-preview

	🤖 Android	🍎 iOS
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