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

Create comprehensive test suite for JibriSession module with 40+ tests
covering all error scenarios from sendIQ callbacks. Extend StropheErrorHandler
tests to validate string error handling, which occurs when Strophe passes
connection-level errors like "Not connected" to error callbacks.

Test coverage includes:
- JibriSession: error parsing (XML, strings, timeouts), start/stop methods,
  success paths, and full recording lifecycle
- StropheErrorHandler: string errors and unknown error types
- Integration testing pattern: utilities run naturally, spy on side effects

Author: hristoterezov