Implements lease-based coordination for Mode B operations:
- LeaderElection service with per-scope leases (reshard, rebalance, etc.)
- ModeBOpLeader<E> generic coordinator with phase state persistence
- Task store support for leader lease operations (SQLite, Redis)
- Mode C coordinator for chunked background jobs
- Reshard/dump chunking modules
Lease semantics:
- TTL 10s, renewed every 3s (configurable)
- New leaders resume from last committed phase after failover
- All Mode B operations are idempotent and resumable
Acceptance tests verified:
- Exactly one leader across multiple pods
- Failover promotes new leader within lease_ttl_s
- Phase recovery after leader loss (reshadow, 2PC)
- Leader metrics consistency (miroir_leader)
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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