Reconcile and dispatch at most one due recipient of an already running task, preserving all call, credit, concurrency and timing guards

Reconciles actual calls and tries to process at most one due recipient of an already running task. Requires the current revision; it never starts or resumes a task. It uses the same calling window, suppression, budget reservation, credit, capacity and atomic claim as cron. The persisted opt-in dispatchOrder: "first_attempts_first" prioritizes due recipients without a counted attempt; pre-dial rejections (countsAsAttempt: false) retain this priority. Existing item order remains the default, and future nextAttemptAt values are respected. Read the current state after an uncertain result instead of blindly repeating a request. Every new logical tick needs a new Idempotency-Key, even when the revision has not changed.