fix(mac): count the HUD timer from the helper's first frame

[EtienneLescot]

Summary

• The macOS start IPC now returns the helper's recording-started timestamp, the instant its first frame reached the file, and the HUD timer counts from it instead of from the reply's arrival. The cursor offset uses the same anchor. A helper that sends no timestamp keeps today's behaviour.
• The ~20 s gap in the report was createdAt (the recording id, stamped before the permission prompts) taken for the start of capture; the stall itself was removed by fix: handle macOS capture permission failures #886.
• Native follow-up, not in this PR: in a picker session, a take whose start stalls past main's 10 s timeout can still start capturing after its stop, because ScreenCaptureRecorder.start() never re-checks shutdownTask after its awaits (the microphone prompt can wait 30 s in ensureRequestedPermissions). Plan: check shutdownTask after each await before setupWriter/startCapture, and align the 30 s wait with main's 10 s.

Related issue

Part of #901

Type of change

• Bug fix

Release impact

• Patch

Desktop impact

• macOS

Testing

• New test in useScreenRecorder.nativeMacStartWarning.test.tsx: a helper stamp 20 s old shows 20 s on the HUD. It fails without the fix.
• vitest --run src/hooks electron/ipc: 147 passed. Both tsc configs and Biome.
• Not done: a take on macOS.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Fixed the elapsed recording timer on macOS so it reflects when capture actually began, rather than when the start request finished. This keeps the timer accurate when there is a delay before the recording-start response arrives.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

• Configuration used: defaults
• Review profile: CHILL
• Plan: Advanced
• Run ID: e8d236ed-2194-4c29-a216-f3789b64f0ea

📥 Commits

Reviewing files that changed from the base of the PR and between 6e27423 and c8da1d7.

📒 Files selected for processing (4)

• electron/ipc/handlers.ts
• src/hooks/useScreenRecorder.nativeMacStartWarning.test.tsx
• src/hooks/useScreenRecorder.ts
• src/lib/nativeMacRecording.ts

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📝 Walkthrough

Walkthrough

The native macOS start flow now passes the helper’s capture-start timestamp through the IPC response. The screen recorder uses that timestamp to initialize elapsed time, with Date.now() as a fallback.

Changes

Native macOS start timing

Layer / File(s)	Summary
Propagate the capture-start timestamp electron/ipc/handlers.ts	The capture-start wait returns a finite helper timestamp or null. The start handler uses the timestamp when available, falls back to Date.now(), and returns it as startedAtMs.
Initialize elapsed time from the start result src/lib/nativeMacRecording.ts, src/hooks/useScreenRecorder.ts, src/hooks/useScreenRecorder.nativeMacStartWarning.test.tsx	The start result adds optional startedAtMs. The recorder uses it to initialize timing. A test checks for 20 elapsed seconds when the start reply arrives 20 seconds after the reported start.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix

Suggested reviewers: arhxam

Merge Risk: 🔵 Low · up to c8da1

The change is mergeable; a system-clock rollback could briefly make the HUD show negative elapsed time, with no evidence of recording loss.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 25.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 4 functions across 4 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely identifies the main change: the macOS HUD timer now starts from the helper’s first-frame timestamp.
Description check	✅ Passed	The description covers the change, related issue, bug-fix and release impact, macOS impact, and testing. The omitted Screenshots / video section is not critical for this non-visual change.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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