Carries forward the non-spin parts of the dropped spin-tooling commit:
- .gitignore: __pycache__/ and *.pyc
- sweep.py: generic vs-tokio comparison summary (no spin_sweep coupling)
The spin_sweep README docs from that commit are intentionally left behind.
The profile was captured against the spin-enabled build. With the RFC 004
spinning experiment excised from master, the ~12% hot-path futex_wake it
attributed to the spinning submit-rule no longer exists (idle wait is back to
thread::sleep). Add a provenance note, mark the futex_wake row/finding as
excised spin machinery, and drop the now-moot 'gate the submit wake' lead.
Spin-independent findings (shims ~1%, schedule_loop + run-queue ~33%) unchanged.