stack/docs/scratchpads/f4-matrix-connector.md

F4 — Orchestrator chat connector + Matrix (#616)

• Issue: #616 · Branch: feat/f4-matrix-connector (off main; independent of #615) · Doctrine: north-star #613.

Phase 1 (this PR) — abstraction + scaffold

• src/fleet/connectors/types.ts: OrchestratorConnector (send/subscribe/health) + message/config types; thread-aware via optional threadId; DEFAULT_CONNECTOR_KIND=tmux.
• src/fleet/connectors/registry.ts: extensible factory registry; resolveConnectorKind (defaults tmux, back-compat); createConnector throws ConnectorNotImplementedError until Phase 2 registers factories.
• roster.schema.json: optional connector block (tmux|discord|matrix; matrix homeserver/user/room; secrets via env, never roster).
• Design doc docs/fleet/f4-matrix-connector.md: interface, config, Matrix CS-API mapping, Conduit-default infra, phasing.
• No fleet.ts changes → self-contained, zero conflict with stacked #615.

Verification

• 7 connector tests green; tsc/eslint/prettier/sanitize clean; schema valid JSON.

Phase 2+ (follow-ups, in the doc)

Matrix CS-API client (fetch send/sync/health) + factory; init/configure connector-selection UX + roster-parse wiring; systemd launch wiring; Conduit deploy guide; first-party Mosaic Discord (threads) as a connector.