#3109 Settle expired signal waits from swamp serve

Problem

Split out of swamp-club#3094. A wait_for_signal deadline is noticed only when something looks: workflow signal, workflow waits and workflow resume each settle an overdue wait as timed_out (outcomeAt in src/domain/workflows/signal_wait_cleanup.ts). Under swamp serve nothing looks, so an expired wait stays suspended and its failed handlers do not run until someone resumes the run.

Proposal

• The continuation sweep of swamp-club#3108 also lists registered waits and, for each one past its deadline with no outcome, creates a timed_out outcome and attempts continuation. Every instance may sweep; the create decides between a timeout and a signal arriving at the same moment.
• After downtime, overdue waits are caught up on the first sweep. The deadline is absolute; how soon the handlers run depends on serve being up.
• A maximum timeout configured on serve. Today one year is hard-coded in the task schema.

Open decisions

1. The maximum timeout: where it is enforced (when the workflow is validated, or when the wait opens) and what happens to a wait already open with a longer one.
2. Whether an expired approval gate should be failed by the sweep. Today it stays suspended (evaluateApprovalTimeout is checked only on approve, reject and listing); changing it alters existing workflows.
3. Whether the sweep settles waits on a custom datastore, where this host may not have the run record. Settling needs only the registration; continuing needs the run.

Acceptance criteria

• A wait past its deadline fails its step with wait_timeout, and its failed handler runs, with no client action.
• Waits that expired while serve was down are settled on the first sweep after boot.
• A signal accepted before the deadline still holds when the sweep runs after it.

Tests

• Integration tests with a fake clock and ordered creates, never sleeps: signal against timeout, deadline catch-up after downtime, two instances sweeping the same wait.

Depends on

swamp-club#3108 (continuation claim and sweep). Without it a timed-out wait would be settled but its run not resumed.

References

swamp-club#3094, swamp-club#3093, the Timing out paragraph of the Wait for Signal section in design/primitives/workflows.md.