feat(go-services): Phase 2 ingest — shared Ingestor + shadow consumer

Implements the plugin event handlers (the /ws/position write logic) as a shared
Ingestor, validated against real traffic by replaying Python's /ws/live firehose
into an isolated dereth_go DB (no production write, no plugin stolen).

- ingest.go: faithful ports of telemetry (kill-delta -> char_stats, server
  received_at stamp), rare (rare_stats/rare_stats_sessions/rare_events), portal
  (coord upsert), character_stats (stats_data JSONB subset + upsert), spawn, and
  the memory-only handlers (vitals/quest/equipment_cantrip/nearby/dungeon). In
  -memory live state + read-side overlay accessors.
- shadow.go: coder/websocket consumer of /ws/live -> Ingestor.dispatch (telemetry
  matched by shape since its broadcast has no type field).
- main.go/store.go: ingest mode (READ_ONLY=false + SHADOW_INGEST_WS) wires the
  ingestor; read handlers (/character-stats, /equipment-cantrip, /quest-status)
  now consult the live overlay first, like Python.
- compose: shadow instance ingests ws://dereth-tracker:8765/ws/live.

Validated live: dereth_go has 73 distinct telemetry chars; shadow /live online
set == production (73=73); character_stats 5/5 exact byte-match (0 mismatch);
char_stats kill-deltas + portals accumulating. compare/compare_ingest.py.

Deferred to next pass: combat_stats (delta/merge), share_*, the /ws/position +
/ws/live servers (for cutover).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

go-services/docker-compose.go.yml

@@ -110,7 +110,8 @@ services:
       READ_ONLY: "false"           # owns its DB; creates schema on boot
       INVENTORY_SERVICE_URL: "http://inventory-service:8000"
       SECRET_KEY: "${SECRET_KEY}"
-      # SHADOW_INGEST_WS: "ws://dereth-tracker:8765/ws/live"  # enabled once ingest handlers land
+      # Replay the Python /ws/live firehose into the ingest handlers (shadow).
+      SHADOW_INGEST_WS: "ws://dereth-tracker:8765/ws/live"
       LOG_LEVEL: "INFO"
     depends_on:
       - dereth-go-db