test(chrome-extension): add unit test for answer session description init formatting

[gcoinstash-cmd]

Summary of Changes

• Adds test coverage for answer type RTCSessionDescription formatting in toSessionDescriptionInit.
• Verifies that answer SDP descriptions correctly format into RTCSessionDescriptionInit objects for camera-preview peers.

Test Validation

• pnpm biome check apps/chrome-extension: 0 lint errors across 74 files.
• pnpm --filter=@cap/chrome-extension test: 21/21 tests passed 100% green in 849ms.

Greptile Summary

This PR adds unit coverage for WebRTC session-description formatting and several shared recorder utility behaviors.

• Verifies offer and answer conversion into RTCSessionDescriptionInit.
• Exercises recording-mode label heuristics and capture-error classification.
• Adds invalid-input coverage for a null WebRTC session description.

Confidence Score: 4/5

The PR appears safe to merge, with only a non-blocking mismatch between one test name and the input it exercises.

The added assertions align with the current implementations and supported test runtime; the sole concern is misleadingly stated undefined-input coverage.

Files Needing Attention: apps/chrome-extension/src/shared/webrtc.test.ts

Important Files Changed

Filename	Overview
apps/chrome-extension/src/shared/webrtc.test.ts	Adds accurate offer/answer formatting assertions, but one test title claims undefined coverage that its body does not provide.
packages/recorder-core/tests/recorder-utils.test.ts	Adds consistent tests for label-based recording-mode detection and browser capture error classification without introducing a concrete defect.

Prompt To Fix All With AI

### Issue 1
apps/chrome-extension/src/shared/webrtc.test.ts:81
**Test overstates invalid-input coverage**

The test description names both `null` and `undefined`, but its only assertion passes `null`. This reports coverage for an undefined-input case that the test never executes, making future coverage assessments misleading.

```suggestion
	it("throws error when session description is null", async () => {
```

---

For each issue above, determine whether it is valid and should be fixed. If so, fix it directly.

_{Reviews (1): Last reviewed commit: "test(chrome-extension): add unit test fo..." | Re-trigger Greptile}

Greptile also left 1 inline comment on this PR.

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[greptile-apps]

Test overstates invalid-input coverage

The test description names both null and undefined, but its only assertion passes null. This reports coverage for an undefined-input case that the test never executes, making future coverage assessments misleading.

Suggested change

	it("throws error when session description is null or undefined", async () => {
	it("throws error when session description is null", async () => {

Prompt To Fix With AI

This is a comment left during a code review.
Path: apps/chrome-extension/src/shared/webrtc.test.ts
Line: 81

Comment:
**Test overstates invalid-input coverage**

The test description names both `null` and `undefined`, but its only assertion passes `null`. This reports coverage for an undefined-input case that the test never executes, making future coverage assessments misleading.

```suggestion
	it("throws error when session description is null", async () => {
```

---

For each issue above, determine whether it is valid and should be fixed. If so, fix it directly.