feat: add confirm_identity API endpoint

- Add POST /api/v1/agents/identity/confirm endpoint
- Calls confirm_identity.py to bind trace to identity
- Updates TKG, Qdrant _faces, PG face_detections, _seeds
- Optional Round 2 propagation after confirmation
- Fix trace_id=0 check in confirm_identity.py (use 'is not None')
- Document API endpoint in 08_identity_agent.md

docs_v1.0/API_WORKSPACE/modules/08_identity_agent.md

@@ -65,4 +65,63 @@ curl -s -X POST "$API/api/v1/agents/identity/match-from-trace" \
 ```
 
 ---
-*Updated: 2026-05-19 12:49:24*
+
+### `POST /api/v1/agents/identity/confirm`
+
+**Auth**: Required
+**Scope**: file-level
+
+Confirm identity binding for a trace. This marks the trace as confirmed in TKG, updates face_detections, adds to _seeds, and optionally triggers Round 2 propagation.
+
+#### Request Parameters
+
+| Field | Type | Required | Description |
+|-------|------|----------|-------------|
+| `file_uuid` | string | Yes | Video file UUID |
+| `trace_id` | integer | Yes | Face trace ID to confirm |
+| `identity_id` | integer | Yes | Identity internal ID |
+| `identity_uuid` | string | Yes | Identity UUID |
+| `name` | string | Yes | Identity name |
+| `propagate` | boolean | No | Auto-trigger Round 2 matching (default: true) |
+
+#### Example
+
+```bash
+curl -s -X POST "$API/api/v1/agents/identity/confirm" \
+  -H "Authorization: Bearer $JWT" \
+  -H "Content-Type: application/json" \
+  -d '{"file_uuid": "'"$FILE_UUID"'", "trace_id": 10, "identity_id": 42, "identity_uuid": "'"$IDENTITY_UUID"'", "name": "Cary Grant", "propagate": false}'
+```
+
+#### Response (200)
+
+```json
+{
+  "success": true,
+  "file_uuid": "384b0ff44aaaa1f1",
+  "trace_id": 10,
+  "identity_uuid": "a9a90105...",
+  "name": "Cary Grant",
+  "steps": {
+    "tkg_updated": true,
+    "qdrant_updated": 150,
+    "pg_updated": 150,
+    "seed_added": true
+  },
+  "propagation": {
+    "matched": 5,
+    "message": "Propagation completed"
+  }
+}
+```
+
+#### Side Effects
+
+1. TKG face_track node status → 'confirmed'
+2. Qdrant _faces: identity_uuid added to payload
+3. PG face_detections: identity_id set
+4. Trace centroid added to _seeds (source='propagation')
+5. Round 2 matching triggered (if propagate=true)
+
+---
+*Updated: 2026-06-26 00:30:00*