Replace subprocess.run(capture_output=True) with Popen + line-by-line
iteration so every line from multitrack_runner.py appears in the nohup
log immediately rather than only after the trial completes (~35-90 min).
- stdout/stderr merged via stderr=STDOUT
- line-buffered (bufsize=1)
- deadline-based timeout replaces subprocess timeout kwarg
- output accumulated in list for parse_runner_output() as before
Agent: pi
Tests: 30 passed
Tests-Added: 0
TypeScript: N/A
Paul Huliganga