Adds the per-instance Redis Stream consumer group (live-broadcast-{instance_id})
that reads the telemetry stream and fans out each position to subscribed
WebSocket connections without affecting the durable-write consumer path.
Key changes:
- src/shared/codec.ts: moved decodePosition/CodecError out of src/core/ so
src/live/broadcast.ts can decode positions without crossing the enforced
src/core/ ↔ src/live/ boundary; src/core/codec.ts now re-exports from there
- src/shared/types.ts: added Position and AttributeValue (same move, same reason);
src/core/types.ts re-exports both to preserve existing import paths
- src/live/broadcast.ts: createBroadcastConsumer factory — XREADGROUP loop,
immediate ACK semantics, toPositionMessage mapper, fanOut per event/topic
- src/live/device-event-map.ts: createDeviceEventMap factory — in-memory cache
of entry_devices × entries join, refreshed every LIVE_DEVICE_EVENT_REFRESH_MS
- src/db/migrations/0002_positions_faulty.sql: adds faulty boolean column and
positions_device_ts_idx for snapshot-on-subscribe query (task 1.5.5)
- src/main.ts: wired authClient, authzClient, registry, liveServer,
deviceEventMap, broadcastConsumer; shutdown chain: liveServer → deviceEventMap
+ broadcastConsumer → durable-write consumer → metricsServer → Redis → Postgres
- test/live-broadcast.test.ts: 4 unit tests covering single subscriber, multiple
subscribers, orphan device, and multi-event device fan-out
