concurrency-controllisted

# Concurrency Control Use only after the active phase identifies a shared durable-state race. Inherit its authority, artifact, review, proof, output, and completion contract; do not select a work or operational mode here. Core invariant: name the contested state and breaking schedule, then choose the weakest mechanism that closes it at the real isolation boundary. Any expiring exclusive holder is stale-capable and must be fenced or made idempotent. Load one branch: - contested state, writers, or breaking schedule -> [interleavings.md](references/interleavings.md); - conditional write, constraint, optimistic/pessimistic lock, or serializable arbitration -> [arbitration.md](references/arbitration.md); - conflict retry, lease, fencing, leader, or singleton overlap -> [conflicts-and-fencing.md](references/conflicts-and-fencing.md).