Fix three tester findings on T5:
1. RF2 with missing replicas now reports "degraded" instead of
"no_replicas". Only RF=1 with no replicas returns "no_replicas".
Missing replica in an RF2 set is a degraded cluster state.
2. TransportDegraded signal now incorporated: if master-observed
transport is degraded, ClusterReplicationMode is at least
"degraded" regardless of individual replica health.
3. API surface exposure: EngineProjectionMode and
ClusterReplicationMode now appear on blockapi.VolumeInfo and are
populated in entryToVolumeInfo(). Operators can consume both
through GET /block/volume/{name} with distinct JSON field names.
12 tests: keepup, catching_up, stale degraded, LSN gap needs_rebuild,
rebuilding role, RF1 no_replicas, RF2 missing degraded, transport
degraded, distinctness, heartbeat update, worst dominates, API
surface distinct naming.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
pingqiuandClaude Opus 4.6
ceb68cc66b