docs: commit all Phase 6 documentation updates and OpenSpec archives

- devops docs: 8 files updated for Phase 6 state; field-trial.md added (946-line runbook)
- developer docs: api-reference (50+ endpoints), quick-start, 5 existing guides updated, 5 new guides added
- engineering docs: all 12 files updated (services, architecture, SDK guide, testing, overview)
- OpenSpec archives: phase-7-devops-field-trial, developer-docs-phase6-update, engineering-docs-phase6-update
- VALIDATOR.md + scripts/start-validator.sh: V&V Architect tooling added
- .gitignore: exclude session artifacts, build artifacts, and agent workspaces

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docs/developers/guides/query-audit-logs.md

@@ -25,6 +25,11 @@ Every action below is automatically recorded. You cannot create, modify, or dele
 | `credential.revoked` | Successful `DELETE /agents/{agentId}/credentials/{credentialId}` |
 | `auth.failed` | Failed authentication attempt on `POST /token` |
 
+> **Audit chain verification**: In addition to querying events, you can verify the cryptographic
+> integrity of the entire audit hash chain via `GET /api/v1/audit/verify`. This endpoint requires
+> `audit:read` scope and is rate-limited to 30 requests/min. See the
+> [API Reference](../api-reference.md#get-auditverify---verify-audit-chain-integrity) for details.
+
 ---
 
 ## Query the audit log