SessionInput admission, retry, and wake intent

Validate inbox ID reuse before mutating wake state: require exact Session, encoded prompt, and delivery equality; every conflict must leave the row unchanged. An exact retry may upgrade durable wake intent, and explicit resume of resume:false must arm only that ordinary pending input before claim acquisition; promoted rows, conflicts, and recovery continuations remain inert. SessionInput.admit returns { admitted, shouldWake }, and callers wake only from durable eligibility.