flow/gc drops terminal (done/cancelled) records, keeps live suspended flows, returns
count removed; flow/forget id drops one terminal record and refuses live flows.
Bounds unbounded store growth (retention/GC). Bumped conformance sx_server timeout
to 540s for the 10-suite run under CPU contention. 151/151 across 10 suites.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
