fix(schedule): harden calendar transition handling

.agents/notes/implemented/feature/2026-08-05-durable-web-schedule.md

@@ -66,7 +66,7 @@ The persistence coordinator supplies that acknowledgement only after its write p
 
 ### Live delivery lifecycle
 
-The Agent-scoped owner derives its active targets and latest recurring batch from the durable fold. Long targets use bounded timer segments, and every wake reads the wall clock again, so a rollback cannot fire early and a forward jump becomes overdue. A fixed-rate record treats its current `scheduledAt` as the earliest unaccepted point on the original sequence; integer division selects the latest due point directly. A Cron record treats its persisted target as a history-stable baseline, searches only for newer current matches, and persists the chosen occurrence and next target. Neither rule replays a missed backlog or shifts its authority to delivery time. Once one recurring record is overdue behind a closed gate, the owner arms that gate or an earlier one-shot instead of waking at intervening recurring targets. If a turn or another maintenance task already owns the Agent, `runMaintenance()` rejects the claim; the record stays active and one `whenIdle()` wait triggers a later retry. A rejected persistence preflight or contained framing/synchronous-enqueue failure also leaves the record active, but no private retry timer runs; later Agent activity reaching idle or a successful Schedule management preflight asks the owner to try again.
+The Agent-scoped owner derives its active targets and latest recurring batch from the durable fold. Long targets use bounded timer segments, and every wake reads the wall clock again, so a rollback cannot fire early and a forward jump becomes overdue. A fixed-rate record treats its current `scheduledAt` as the earliest unaccepted point on the original sequence; integer division selects the latest due point directly. A Cron record treats its persisted target as a history-stable baseline, searches only for newer current matches, and persists the chosen occurrence and next target. Neither rule replays a missed backlog or shifts its authority to delivery time. Once one recurring record is overdue behind a closed gate, the owner arms that gate or an earlier one-shot instead of waking at intervening recurring targets. If a turn or another maintenance task already owns the Agent, `runMaintenance()` rejects the claim; the record stays active and one `whenIdle()` wait triggers a later retry. A rejected persistence preflight, contained current-calendar resolution failure, or contained framing/synchronous-enqueue failure also leaves the record active, but no private retry timer runs; later Agent activity reaching idle or a successful Schedule management preflight asks the owner to try again.
 
 The accepted path first clears pending persistence and claims the true idle phase through `runMaintenance()`. Inside that task it refolds the exact Session suffix so a direct management mutation that won the claim race cannot be followed by a stale dispatch, then samples the decision clock once. A due one-shot bypasses the recurring gate and keeps the single fixed frame plus id-only dispatch. Otherwise the 300-second gate admits every overdue Every and Cron record in target/create order: the owner derives each latest occurrence, constructs the complete JSON batch before enqueue, synchronously queues one `followup()`, and appends an independent rule-specific dispatch per record. The gate's spacing directly limits every half-open 24-hour window to at most 288 recurring model turns; no second counter or quota exists. Waking input remains parked until maintenance settles, so the driver cannot claim the message before dispatch enters the log; only after the task releases the phase does the owner wait for the shared dispatch barrier. A framing or synchronous enqueue failure is contained and appends no dispatch. An append failure faults that owner because the message may already be queued. A later prompt-admission, request-checkpoint, or model failure cannot retract a dispatch.