fix(outbox): reclaim stale claims — a crash mid-dispatch stranded events forever

Chasing the e2e flakiness turned up a production durability bug, not a test
bug.

The dispatcher claims an outbox row, executes it, then either deletes it
(success) or reschedules it (failure) — both of which clear the claim. If
the PROCESS DIES in between, neither runs. And `claim_due` only ever selects
`claimed_at IS NULL`. Nothing else in the codebase clears `outbox.claimed_at`
— grep it: there are exactly three writers, and those are two of them.

So a crash or restart mid-dispatch stranded every in-flight row PERMANENTLY.
Its trigger never fired and no retry could notice. The outbox is the
universal trigger path, so the loss covered kv / docs / files / cron /
pubsub / email / invoke_async / dead-letter alike. This is the same
durability class as the audit's #6 (lost trigger event), which was just
fixed at the WRITE end — this is the same hole at the READ end.

Every other claim-based store already had the safety net: `queue_messages`
and `group_queue_messages` have `reclaim_visibility_timeouts`,
`workflow_steps` has its own reclaim. The outbox was the one that didn't.

`OutboxRepo::reclaim_stale_claims(timeout)` returns rows whose claim is older
than `PICLOUD_OUTBOX_CLAIM_TIMEOUT_SEC` (default 600s), run from the
dispatcher's existing reclaim ticker. The default is deliberately generous —
a script may run for up to 300s (the `scripts.timeout_seconds` CHECK), so a
claim held past twice that is abandoned rather than slow; reclaiming a row a
LIVE dispatcher is still working on would double-execute it (survivable —
dispatch is at-least-once — but not worth courting).

A reclaim does NOT bump `attempt_count`: the handler never ran, so it must
not consume the row's retry budget, or repeated restarts would dead-letter an
event that executed zero times. (Same reasoning as the transient queue
`release` fixed earlier in this branch.)

This is also the root cause of the flaky e2e suites: each test drops its
dispatcher, and `claim_due` is not scoped per app or per dispatcher, so a
test's dispatcher could claim another test's row and strand it on teardown.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/manager-core/src/invoke_service.rs

@@ -319,6 +319,9 @@ mod tests {
     }
     #[async_trait]
     impl OutboxRepo for CapturingOutbox {
+        async fn reclaim_stale_claims(&self, _timeout_secs: u32) -> Result<u64, OutboxRepoError> {
+            Ok(0)
+        }
         async fn insert(&self, row: NewOutboxRow) -> Result<uuid::Uuid, OutboxRepoError> {
             let id = uuid::Uuid::new_v4();
             *self.last.lock().await = Some(row);