Phase 12.L.E.7.2 — fix: bump healthz retries=10 for python3 spawn timing
Summary
Second-iteration fix for J.L.E.7 Linux runner. Previous fix (J.L.E.7.1) resolved systemctl-restart-wrong-unit. New failure: healthz check fails because python3 responder needs ~500ms-2s to bind a port, but retries=1 gives <1s.
Fix
Bump HEALTHCHECK_RETRIES from 1 to 10. ~10-15s window — well under production's 90s default but generous enough for python3 startup variance.
Why this is fine
Test-only timing tweak. Production .sh runs with 90 retries (default). The test seam just balances fast-enough vs reliable-enough.