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/manage-credentials.md

@@ -2,6 +2,11 @@
 
 A credential is a `client_id` + `client_secret` pair that your agent uses to get access tokens. This guide covers all four credential operations.
 
+> **Multi-tenant note**: Credentials issued for an agent that belongs to an organization will
+> produce tokens carrying an `organization_id` claim. This claim is required by analytics,
+> webhooks, tier enforcement, and A2A delegation. Ensure your agent is registered with
+> `organization_id` before issuing credentials for production use.
+
 All credential endpoints are under `/api/v1/agents/{agentId}/credentials` and require a Bearer token with `agents:write` scope.
 
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