Make a repeat channel delete a no-op instead of a second announcement and audit row

[Chebaleomkar]

What this changes

softDelete's comment says its deleted_at guard "is what makes a repeat call a no-op rather than a new stamp", and the existing test is "deleting again is a no-op, not an error". The guard kept the timestamp, but the rest of a delete still ran on every repeat:

• the member list was read and pg_notify told every member the channel was deleted, again;
• the route then called recordDeleted, which wrote another channel.deleted row to audit_events. That table is append-only, so a retry, a second tab or a double click left rows for deletions that did not happen. The comment above recordDeleted says "The trail records acts, not attempts."

softDelete now returns whether this call deleted the channel. The update uses .returning(); on zero rows it returns false before reading members or notifying. The route records only when the store did not answer false, and still answers 204 either way, so DELETE stays idempotent for the client.

ChannelStore.softDelete changes from Promise<void> to Promise<boolean>. Test fakes that resolve undefined are treated as "deleted", so existing route tests keep their behaviour. The test files are outside server/tsconfig.json's include.

Where it runs

• New state that outlives a request? None.
• What happens on the second replica? Two replicas deleting at once: the guarded UPDATE ... RETURNING stamps one row once, so exactly one of them announces and records.
• Anything serialised? The existing guarded update is the serialisation; no check-then-write is added.
• Anything fanned out to a browser? The same pg_notify, now only for the call that deleted.
• New listener, port, or schedule? No.

Boundary and audit

• A real deletion still writes its channel.deleted row. A repeat no longer writes one, because nothing happened.
• Nothing new is trusted from the client.

Changelog

• A line under Unreleased.

Proof

Test	upstream routes.ts	this branch
channel-events.integration, new: a repeat delete announces nothing to either member (real LISTEN/NOTIFY, with a 500 ms window)	fail	pass
channel-routes, new: the route answers 204 and writes no audit row when the store answers false	fail	pass
channel-routes, existing "deleting again is a no-op", now asserting true then false	fail	pass

channel-routes, channel-events.integration, runtime-agents.integration and routines-store.integration pass 165 of 165 against pgvector/pgvector:pg17. tsc --noEmit exits 0, and biome is clean.

[davidmckayv]

The current head 99277ff matches the accepted source disposition from the refreshed triage. Required CI must pass before landing.

[davidmckayv]

I pushed one commit to fix the server typecheck. softDelete now returns whether it deleted anything, but the Bot reset's softDeleteChannel hook (server/src/agents/lifecycle-reset.ts) was typed Promise<void>, so server/src/index.ts no longer compiled. The reset ignores the return value, so the hook now accepts any result.