test(recording): Add JibriSession tests and string error handling coverage

[hristoterezov]

Summary

• Created comprehensive test suite for JibriSession module (40+ tests)
• Extended StropheErrorHandler tests to cover string error handling
• Validates error handling improvements for various Strophe sendIQ error types

Test Coverage

JibriSession.spec.ts (new file):

• Error parsing: XML elements, string errors, null/undefined timeouts, edge cases
• start() method: success path, error scenarios (503, 403, timeout, string errors)
• stop() method: success path, various error scenarios
• Integration tests: full recording and streaming lifecycle
• _createIQ method: proper XMPP stanza generation

StropheErrorHandler.spec.ts (extended):

• String error handling ("Not connected", "Connection timeout", etc.)
• Unknown error types (numbers, arrays, objects)
• All errors correctly logged to RTCStats

Test Strategy

Follows codebase integration testing pattern:

• Utilities (handleStropheError, getSessionIdFromIq) run naturally
• Spy on side effects (RTCStats.sendStatsEntry) for verification
• Mock XmppConnection with controlled sendIQ behavior

Test Plan

• All 387 tests pass
• Error handling validated for XML elements, strings, and timeouts
• Integration with handleStropheError verified
• No regressions in existing tests