- the revision is a hand-bumped integer mixed into wireFingerprint and nothing tied it to protocol.fbs's content; scripts/ci/protocol_revision_pin.py holds {revision -> sha256(protocol.fbs)} in protocol_revision_pins.json and refuses a schema whose digest is not the current revision's, or a revision with no row
- registered as ProtocolSchema.RevisionPinsDigest (label unit, MG_Test/Wire/CMakeLists.txt, --self-test proves both perturbations red before it says green) and as a step of CI's flatc-check job, the one that regenerates the header on every schema edit
- --write records a bump's row and refuses to re-pin an existing revision to a different digest, which is what a schema edit without a bump looks like
- mg_protocol_base.h says where the pin lives beside the revision it pins
- red-once: protocol.fbs touched with one trailing comment, revision left at 1 -> "protocol.fbs has sha256 a7b5c7fb... but MOBILEGL_PROTOCOL_CONTROL_REVISION is still 1, which is pinned to 7fc859f7..." rc=1; restored, green
