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/register-an-agent.md

@@ -20,6 +20,7 @@ Requires: `Authorization: Bearer <token>` with `agents:write` scope.
 | `capabilities` | string[] | Yes | One or more capability strings in `resource:action` format. Minimum 1. |
 | `owner` | string | Yes | Team or organisation that owns this agent. 1–128 characters. |
 | `deploymentEnv` | string (enum) | Yes | Target deployment environment. See values below. |
+| `organization_id` | string (UUID) | No | UUID of the organization to scope this agent to. Recommended on all multi-tenant instances. |
 
 ### `agentType` values
 
@@ -70,7 +71,8 @@ curl -s -X POST http://localhost:3000/api/v1/agents \
     "version": "1.0.0",
     "capabilities": ["resume:read", "email:send", "candidate:score"],
     "owner": "talent-acquisition-team",
-    "deploymentEnv": "production"
+    "deploymentEnv": "production",
+    "organization_id": "'$ORG_ID'"
   }' | jq .
 ```
 
@@ -93,6 +95,11 @@ Successful response (`201 Created`):
 
 The `agentId` is assigned by the system — it is immutable and never changes.
 
+> **Organization scoping**: If you include `organization_id` in the request, the agent is
+> associated with that organization. Analytics, webhook events, and tier enforcement are all
+> scoped by organization. To create an organization first, see the
+> [Quick Start](../quick-start.md) guide.
+
 ---
 
 ## Immutable fields