fix: job run command exits with status code 1 on failure.

[aviatco]

✨ Description of new changes

Fix #128
This pull request fixes the behavior of the job run command so that it properly exits with status code 1 when a job fails, and adds comprehensive unit tests to verify error handling. The main changes focus on error reporting and test coverage for job failures.

Error handling improvements:

• Modified wait_for_job_completion in fab_cmd_job_utils.py to raise a FabricCLIError with ERROR_JOB_FAILED when a job status is 'Failed', ensuring the CLI exits with code 1 on failure.
• Updated the unreleased changes log to document the fix for proper exit status on job run failure. (.changes/unreleased/fixed-20260112-143553.yaml)

Testing enhancements:

• Added three new unit tests to test_jobs.py to verify that job failures (including with a timeout) correctly raise FabricCLIError and result in exit code 1, improving confidence in error handling for failed jobs.
• Imported FabricCLIError in test_jobs.py to support new failure-handling tests.