Pulls in the coarse-pacing fix for parked wait-for-operator states (a
machine left in Door or Hold no longer pins ~28% of the core), plus
P10's grblHAL CI/tests and the mlockall-root-only change. Fetch-verified.
Adds pacing_test.py (dry hold/resume + CPU measurement) and records the
diagnosis and bench validation in BRINGUP.
