feat: metrics record --emit-event for kaizen.metrics.recorded

Publish activity-core EventEnvelope payloads to NATS subject
activity.kaizen.metrics.recorded after a successful append.
Optional nats-py via kaizen-agentic[events]; project slug from
KAIZEN_PROJECT_SLUG or directory basename. Skips emit on
idempotency duplicates. Closes KAIZEN-WP-0008 T03.

docs/integrations/activity-definitions/low-success-rate-review.md

@@ -35,9 +35,11 @@ action:
 
 **Threshold:** 0.8 success rate, minimum 5 executions (avoids noise on early pilots).
 
-**CLI mapping:** Event emitter is future work; manual check today:
+**CLI mapping:** `kaizen-agentic metrics record <agent> --emit-event` after each
+append (see [kaizen-metrics-recorded-event.md](../kaizen-metrics-recorded-event.md)).
+Manual check today:
 
 ```bash
 kaizen-agentic metrics show <agent>   # inspect summary.success_rate
 kaizen-agentic metrics optimize <agent>
-```
+```

docs/integrations/kaizen-metrics-recorded-event.md

@@ -0,0 +1,69 @@
+# Event Payload: `kaizen.metrics.recorded`
+
+**Status:** implemented — `kaizen-agentic metrics record --emit-event`
+
+Emitted after a successful metrics append when `--emit-event` is set. Default
+off for backward compatibility.
+
+## Subject
+
+```
+activity.kaizen.metrics.recorded
+```
+
+Published to NATS (activity-core `EventEnvelope` format). Consumed by
+activity-core event router and definitions such as `low-success-rate-review`.
+
+## Envelope
+
+```json
+{
+  "id": "550e8400-e29b-41d4-a716-446655440000",
+  "type": "kaizen.metrics.recorded",
+  "version": "1.0",
+  "timestamp": "2026-06-18T12:00:00Z",
+  "publisher": "kaizen-agentic",
+  "attributes": {
+    "agent": "coach",
+    "project": "kaizen-agentic",
+    "summary": {
+      "success_rate": 0.75,
+      "execution_count": 12,
+      "avg_quality": 0.81
+    }
+  }
+}
+```
+
+### Attribute fields
+
+| Field | Type | Notes |
+|-------|------|-------|
+| `agent` | string | Agent name from `metrics record <agent>` |
+| `project` | string | Repo slug — `KAIZEN_PROJECT_SLUG` env or directory basename |
+| `summary.success_rate` | float | Rolling rate from `summary.json` after append |
+| `summary.execution_count` | int | Total executions |
+| `summary.avg_quality` | float | Maps from `avg_quality_score` in ADR-004 summary |
+
+## CLI
+
+```bash
+kaizen-agentic metrics record coach --success --time 120 --quality 0.9 --emit-event
+```
+
+Requires `nats-py` (`pip install 'kaizen-agentic[events]'`). Configure broker via
+`NATS_URL` (default `nats://localhost:4222`).
+
+Events are **not** emitted when append is skipped (duplicate idempotency key).
+
+## Consumers
+
+- **activity-core** — `trigger.type: event` with `event_type: kaizen.metrics.recorded`
+- **coulomb-loop** — `low-success-rate-review` (LOOP-WP-0002); replaces hourly
+  health sweep when event path is stable
+
+## Related
+
+- [low-success-rate-review](activity-definitions/low-success-rate-review.md)
+- [INTEGRATION_PATTERNS.md Pattern 2](../INTEGRATION_PATTERNS.md)
+- coulomb-loop `loops/quality-escalation/event-payload.md` (customer contract)