Implement Phase 1 tasks 1.5-1.8 (consumer + state + writer + main wiring)

src/core/consumer.ts — XREADGROUP loop with consumer-group resumption,
ensureConsumerGroup (BUSYGROUP-tolerant), decodeBatch (CodecError → log
+ skip + leave pending; never speculative ACK), partial-ACK semantics,
connectRedis (mirroring tcp-ingestion's retry pattern), clean stop.

src/core/state.ts — LRU Map<device_id, DeviceState> using delete+set
bump trick (no third-party LRU dep); last_seen = max(prev, ts) so
out-of-order replays don't regress the high-water mark; evictedTotal()
counter.

src/core/writer.ts — multi-row INSERT ON CONFLICT (device_id, ts) DO
NOTHING with RETURNING. Duplicate detection by set-difference between
input and RETURNING rows (xmax=0 doesn't work for skipped-conflict
rows, only returned ones — confirmed in the task spec's own Note).
Sequential chunking to WRITE_BATCH_SIZE; bigint→string and Buffer→base64
attribute serialization that handles Buffer.toJSON shape.

src/main.ts — full pipeline: pool → migrate → redis → state → writer →
sink → consumer → graceful-shutdown stub. Sink ordering is
state.update BEFORE writer.write per spec rationale (state stays
consistent with what's been seen even if not yet persisted; redelivery
is idempotent on state). Metrics is still the trace-logging shim from
tcp-ingestion's pre-1.10 pattern; real prom-client lands in task 1.9.

Verification: typecheck, lint clean; 112 unit tests passing across 7
test files (+39 from this batch).

.planning/ROADMAP.md

@@ -40,7 +40,7 @@ These rules govern every task. Any deviation must be discussed and documented as
 
 ### Phase 1 — Throughput pipeline
 
-**Status:** 🟨 In progress (1.1–1.4 done; 1.5–1.11 ahead)
+**Status:** 🟨 In progress (1.1–1.8 done; 1.9–1.11 ahead)
 **Outcome:** A Node.js Processor that joins a Redis Streams consumer group on `telemetry:t`, decodes each `Position` (including `__bigint`/`__buffer_b64` sentinel reversal), upserts it into a TimescaleDB `positions` hypertable, updates per-device in-memory state (last position, last seen), `XACK`s on successful write, and exposes Prometheus metrics + health/readiness HTTP endpoints. End-to-end pilot-quality service; no domain logic yet.
 
 [**See `phase-1-throughput/README.md`**](./phase-1-throughput/README.md)
@@ -51,10 +51,10 @@ These rules govern every task. Any deviation must be discussed and documented as
 | 1.2 | [Core types & contracts](./phase-1-throughput/02-core-types.md) | 🟩 | `290a08e` |
 | 1.3 | [Configuration & logging](./phase-1-throughput/03-config-and-logging.md) | 🟩 | `290a08e` |
 | 1.4 | [Postgres connection & `positions` hypertable](./phase-1-throughput/04-postgres-schema.md) | 🟩 | `290a08e` |
-| 1.5 | [Redis Stream consumer (XREADGROUP)](./phase-1-throughput/05-stream-consumer.md) | ⬜ | — |
-| 1.6 | [Per-device in-memory state](./phase-1-throughput/06-device-state.md) | ⬜ | — |
-| 1.7 | [Position writer (batched upsert)](./phase-1-throughput/07-position-writer.md) | ⬜ | — |
-| 1.8 | [Main wiring & ACK semantics](./phase-1-throughput/08-main-wiring.md) | ⬜ | — |
+| 1.5 | [Redis Stream consumer (XREADGROUP)](./phase-1-throughput/05-stream-consumer.md) | 🟩 | *(pending commit SHA)* |
+| 1.6 | [Per-device in-memory state](./phase-1-throughput/06-device-state.md) | 🟩 | *(pending commit SHA)* |
+| 1.7 | [Position writer (batched upsert)](./phase-1-throughput/07-position-writer.md) | 🟩 | *(pending commit SHA)* |
+| 1.8 | [Main wiring & ACK semantics](./phase-1-throughput/08-main-wiring.md) | 🟩 | *(pending commit SHA)* |
 | 1.9 | [Observability (Prometheus metrics + /healthz + /readyz)](./phase-1-throughput/09-observability.md) | ⬜ | — |
 | 1.10 | [Integration test (testcontainers Redis + Postgres)](./phase-1-throughput/10-integration-test.md) | ⬜ | — |
 | 1.11 | [Dockerfile & Gitea workflow](./phase-1-throughput/11-dockerfile-and-ci.md) | ⬜ | — |