A wedged Relay pipeline made every compaction block for SCOPE_OP_TIMEOUT
(10s) while it still held the compression lease, with no breaker. The
first stalled mark now trips a process-wide flag and later marks return
immediately; marks are observability and must never tax compaction.
Also: make relay_runtime.SCOPE_OP_TIMEOUT public (relay_compaction reads
it), fold the commit-time telemetry hold into _hold_attempt_telemetry
with one _ATTEMPT_TELEMETRY_FIELDS tuple, and drop the mapping-table
change-detector tests (the ATOF freshness and failure invariants stay).
f925b01791