fix(recording): avoid duplicate system audio fallback

[meiiie]

Summary

• When a recording MP4 already has an embedded audio stream, only include microphone companion audio in the fallback path list.
• Avoid adding recording.system.wav next to the embedded video audio, which duplicates source/system audio candidates.

Why

getCompanionAudioFallbackInfo() was still returning both recording.system.wav and recording.mic.wav when the video itself already contained an audio stream. That contradicted the existing test expectation and can make downstream audio fallback/mux planning consider duplicate system audio.

This is a small extraction from the broader #504 work, separated so we do not merge the stale NVIDIA/export route planner PR as one large change.

Validation

• npm test -- electron/ipc/recording/diagnostics.test.ts (11 passed)
• npx tsc --noEmit
• npx biome check --formatter-enabled=false electron/ipc/recording/diagnostics.ts electron/ipc/recording/diagnostics.test.ts
• git diff --check

Note: npx biome check with formatter enabled wants to rewrite existing CRLF line endings across these files, so I used formatter-disabled scoped Biome to avoid unrelated formatting churn.

Summary by CodeRabbit

• Bug Fixes
  • Improved companion audio fallback path selection when embedded audio streams are detected, ensuring the correct fallback option is used during recording.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: 3bee3c98-f9b5-44f7-8b02-51240a08cb35

📥 Commits

Reviewing files that changed from the base of the PR and between 7fe818f and 059544d.

📒 Files selected for processing (1)

• electron/ipc/recording/diagnostics.ts

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📝 Walkthrough

Walkthrough

The change constrains the fallback companion audio path selection in getCompanionAudioFallbackInfo to use only the microphone path when an embedded audio stream is detected, removing system audio from that fallback candidate set.

Changes

Embedded Audio Companion Path Filtering

Layer / File(s)	Summary
Embedded audio usable paths constraint electron/ipc/recording/diagnostics.ts	When an embedded audio stream is detected, the usablePaths filter for companion audio fallback is tightened to include only candidate.micPath, excluding candidate.systemPath. This constraint affects the resulting paths array and the computed startDelayMsByPath for that embedded-audio case.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Possibly related PRs

• webadderallorg/Recordly#280: Both PRs adjust embedded-audio fallback path selection in electron/ipc/recording/diagnostics.ts to filter down to candidate.micPath, with #280 adding test coverage for that case.

Suggested labels

Checked

Poem

🐰 One path to pick, the microphone's call,
When audio streams are embedded in all,
System sound step back, the mic takes the lead,
A focused companion is all that we need!
✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	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 'fix(recording): avoid duplicate system audio fallback' accurately summarizes the main change—preventing duplicate system audio in companion fallback paths when embedded audio is detected.
Description check	✅ Passed	The PR description covers the key required sections including summary, motivation, type of change (bug fix context), validation steps, and addresses the underlying issue clearly.
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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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/embedded-audio-companion-fallback

Warning

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🔧 ESLint

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