[chiragjangiir]

Closes #72

Summary

This PR addresses issue #72 by adding comprehensive unit test coverage for devagent/background/jobs.py.

Changes

1. Safety Fix: In devagent/background/jobs.py:_is_running, added a guard for pid <= 0 returning False. On POSIX systems, calling os.kill(0, 0) checks if the calling process group is alive, which would incorrectly report invalid/dummy PID 0 as running.
2. Unit Tests Added (tests/test_background_jobs.py):
   • test_is_running_invalid_pid: tests that PID 0 and negative PIDs are safely identified as not running.
   • test_launch_creates_state_and_log_files: tests state and log initialization upon job launch.
   • test_poll_running_process: tests poll state when a background process is still active.
   • test_poll_exit_zero: tests exit state resolution and file persistence when the process exits cleanly.
   • test_poll_exit_nonzero: tests exit state resolution when the process fails with non-zero code.
   • test_poll_exit_no_journal: tests fallback to unknown when no exit journal file exists.
   • test_list_jobs_empty & test_list_jobs_mixed: tests listing multiple background jobs in varying states.

Verification

• Ran pytest tests/test_background_jobs.py (11/11 tests pass in 0.06s).

[knight22-21]

Thanks for the tests, @chiragjangiir! Adding comprehensive lifecycle, polling, and PID validation coverage tests for the background job manager.