🤖 perf: let React Compiler compile ImmersiveReviewView

[ThomasK33]

Summary

ImmersiveReviewView now compiles under React Compiler and leaves the guard's KNOWN_SKIPPED baseline (17/18 hot components compile). Iterating hunks in immersive review spends about 18% less script time.

Background

Follow-up to the React Compiler coverage stack (#4422, #4425–#4429) and #4439. The compiler skipped the whole component because of ??=, a try/catch/finally in the copy-file handler, three render-time ref writes, and one ref read during render.

Implementation

• oldLineMap ??= … becomes oldLineMap = oldLineMap ?? ….
• The copy-file handler's try/catch/finally uses runWithCatchFinally with the same body, error handler, and cleanup. Early returns keep their meaning because the try was the handler's last statement.
• activeFilePathRef, activeFileContentVersionRef, and handleCopyFileRef are synced in useLayoutEffect instead of during render. Layout effects run in the commit's task, before passive effects, which is the ordering the existing comment requires for isStale().
• selectedLineSummary (render path) read hunkJumpLineRangeRef through getCurrentLineSelection. A state mirror, hunkJumpLineRange, now feeds render. Every ref write also sets the state, next to the cursor/selection updates it batches with, and the hot-path callbacks keep reading the ref, so their identities stay stable. One visible difference: after a comment submit or composer cancel that clears the hunk-jump range while no line selection is active, the "Lines …" label now updates right away. Before, it kept showing the cleared range until the next render.

Validation

• Guard: 17/18 hot components compile (1 known skipped); make static-check green.
• src/browser/features/RightSidebar/CodeReview unit tests (79) and tests/ui/review (14) pass.

Measurements

Electron perf e2e, local, serial, 5 runs each, main at 334a5a6 vs this branch. ScriptDuration per run:

Scenario	main (sorted runs)	this PR (sorted runs)	Median
Immersive hunk iteration, 1500 lines / 150 hunks	343, 351, 355, 356, 440 ms	270, 273, 290, 294, 299 ms	355 → 290 ms
Immersive mark-read, 1000 files	14, 16, 18, 19, 19 ms	14, 14, 20, 25, 26 ms	18 → 20 ms (noise)

Hunk-iteration wall time went from 448 to 376 ms (median). The regular review reopen scenario, which doesn't render this component, moved about 10% between runs, which is this host's noise level. The hunk-iteration ranges don't overlap.

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[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-24T20:03:34.112200Z	a54cc5b	PR opened
🔒 Security Review	✅ Completed 2026-09-24T20:05:06.624474Z	a54cc5b	PR opened

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