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/phase-1-throughput/06-device-state.md

@@ -1,7 +1,7 @@
 # Task 1.6 — Per-device in-memory state
 
 **Phase:** 1 — Throughput pipeline
-**Status:** ⬜ Not started
+**Status:** 🟩 Done
 **Depends on:** 1.2
 **Wiki refs:** `docs/wiki/entities/processor.md` (§ State management)
 
@@ -78,4 +78,4 @@ The interface is built to extend: Phase 2 may add fields, but the existing field
 
 ## Done
 
-(Fill in once complete: commit SHA, brief notes.)
+`src/core/state.ts` — LRU Map using delete+set bump trick, `last_seen = max(prev, position.timestamp)` semantics, `evictedTotal()` counter. `test/state.test.ts` — 14 tests covering new-device creation, session counter increment, LRU eviction at cap, LRU re-touch, evictedTotal, out-of-order timestamp rejection, get/size. *(pending commit SHA)*