[codex] Harden sweep cleanup follow-up - #2

Summary

Follow-up to PR #1 after Copilot/Claude review. This hardens sweep shutdown and instrument-output safety, fixes autosave error semantics, improves cleanup diagnostics, and adds targeted regression coverage for the review findings.

Key changes

• Keep AWG output off during static configuration and frequency changes; enable output only after amplitude/frequency/timebase are prepared for acquisition.
• On shutdown timeout, emit SHUTDOWN_TIMEOUT and still force known AWG output off plus close known ports.
• Clean up opened ports if worker startup fails before the sweep thread starts.
• Treat auto-save failures as AUTO_SAVE_FAILED warnings instead of converting a completed sweep into SweepFailed.
• Propagate real adapter close failures to the task runner warning path.
• Include exception type in sweep failure/warning messages.
• Fix single-point reference interpolation and add focused validator/calibration/runtime regression tests.
• Tighten dependency upper bounds and document runtime root / cleanup-warning operator behavior.

Validation

• PYTHONPATH=src .venv/bin/python -m unittest discover -s tests -> 44 tests OK
• PYTHONPATH=src python3 -m unittest discover -s tests -> 44 tests OK
• PYTHONPATH=src .venv/bin/python -m compileall -q src tests -> OK
• python3 -c 'import pathlib, tomllib; tomllib.loads(pathlib.Path("pyproject.toml").read_text())' -> OK
• git diff --check -> OK
• Mac Tk GUI smoke through app.bootstrap.build_desktop_app() -> OK
• Claude -p read-only regression review over runtime fixes -> clean
• Claude -p read-only regression review over tests/docs/dependencies -> clean