test(chrome-extension): verify WebRTC session description formatting

[gcoinstash-cmd]

Summary of Changes

• Adds unit test coverage for WebRTC session description exchange in Chrome extension recording pipeline.
• Test suite passed 100% green.

Greptile Summary

This PR expands unit coverage for Chrome-extension WebRTC session-description conversion and shared recorder utilities.

• Tests offer, answer, and missing WebRTC session descriptions.
• Tests recording-mode label heuristics and display-capture error classification.

Confidence Score: 4/5

The PR appears safe to merge, with one non-blocking test-coverage mismatch to correct.

The added tests are compatible with the configured runtime and existing module resolution, but the WebRTC test advertises undefined coverage without actually passing undefined.

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 focused session-description conversion tests, but the stated undefined edge case is not exercised.
packages/recorder-core/tests/recorder-utils.test.ts	Adds valid coverage for recording-mode detection and cancellation/retry error classification without introducing a concrete failure.

Prompt To Fix All With AI

### Issue 1
apps/chrome-extension/src/shared/webrtc.test.ts:81-83
**Undefined case remains untested**

This test names both `null` and `undefined` as covered inputs but invokes only `null`, so it does not provide the stated regression coverage for `undefined` handling.

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

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[greptile-apps]

Undefined case remains untested

This test names both null and undefined as covered inputs but invokes only null, so it does not provide the stated regression coverage for undefined handling.

Prompt To Fix With AI

This is a comment left during a code review.
Path: apps/chrome-extension/src/shared/webrtc.test.ts
Line: 81-83

Comment:
**Undefined case remains untested**

This test names both `null` and `undefined` as covered inputs but invokes only `null`, so it does not provide the stated regression coverage for `undefined` handling.

---

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