Broadcast committed chat events over authenticated WebSockets and support horizontal fan-out and reconnect recovery.
## Description
Use HTTP/tRPC for commands and Postgres as the source of truth. Consume the outbox contract and atomic writes established by the persistence task; do not create a second message transaction. A worker claims and publishes normalized events through Redis to authenticated WebSocket subscribers. Each channel uses its own `(channel_id, sequence)` cursor, and clients reconnect by replaying missed rows from Postgres per authorized channel. Reuse Hocuspocus/Yjs only for presence, typing, or drafts rather than canonical history.
## Subtasks
- [ ] Finalize one versioned envelope for message, reply, tombstone, channel lifecycle, membership, and read-state events using the existing outbox contract.
- [ ] Add subscriptions/replay using workspace AND context AND channel access; recheck at delivery, close revoked subscriptions, and test that removed access never receives subsequent payloads. No same-workspace-only shortcut or unsupported-object fallback.
- [ ] Claim and publish outbox events through Redis with retry and idempotent consumption semantics.
Operator reports 14/14 live acceptance checks passed on CT 116 via `wss://chat.stillwell.cloud/chat`, including two-member messaging/replies, reconnect, unread, edit/delete recovery and revocation. CT 102 ledger is reported at 24 through `0023`, with Chat tables owned by `echodo`. Evidence is in `docs/Current Progress.md` (operator-supplied; not rerun here). Local regression tests cover projection/redaction fixes and hardened configured-origin ticket checks. Next deployment must rebuild web and retest; keep task in progress pending full checks/final review and unverified outage/multi-instance criteria.
- Extended the existing collab service with Chat secret/port wiring, dual-listener liveness checks, standalone publication, web build URL, and Traefik TLS example. Public build variables now participate in Turbo build inputs.
- Added `scripts/chat-deployment.test.mjs` to the root test command; all five configuration checks pass. This is not live transport acceptance.
- CT 116 access blocked on trusted SSH host-key verification; no migrations or deployment performed. Production schema and disposable-Postgres, Redis outage, reconnect/revocation and two-browser gates remain open. See `docs/deployment-production.md` and `docs/Current Progress.md`.
2026-10-26: Implement signed, scoped short-lived subscription tickets and metadata-only WebSocket invalidation hints. Recheck current Postgres authorization at subscribe, delivery, and heartbeat; reconnect must recover edits/tombstones independently of creation-sequence catch-up. Do not reuse the legacy decode-only Yjs identity as Chat authentication.
