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>

openspec/changes/archive/engineering-docs-phase6-update/proposal.md

@@ -0,0 +1,37 @@
+# OpenSpec Proposal — engineering-docs-phase6-update
+
+**Status:** Approved
+**Proposed:** 2026-04-04
+**Approved by:** CEO
+
+## Problem Statement
+
+`docs/engineering/` (12 files) was written during Phase 2. Nine new services, the Rust SDK,
+14 new DB migrations, and significant architectural changes shipped across Phases 3–6 with
+zero coverage in the engineering documentation. The engineering team cannot onboard or maintain
+Phase 3–6 features without accurate internal docs.
+
+## Workstreams
+
+### WS1 — 05-services.md
+Add deep dives for all 9 Phase 3–6 services: AnalyticsService, TierService, ComplianceService,
+A2AService, FederationService, DIDService, OIDCService, WebhookService, BillingService.
+Each deep dive must match the format of existing service entries (purpose, public methods,
+dependencies, configuration, Redis/DB usage).
+
+### WS2 — 02-architecture.md
+Update the component diagram to include the Next.js portal, analytics pipeline, tier enforcement
+layer, and all Phase 3–6 services. Update data-flow descriptions.
+
+### WS3 — 11-sdk-guide.md
+Add a complete Rust SDK section (sdk-rust/) covering installation, authentication, agent
+registration, token issuance, error handling, and the contribution guide extension.
+
+### WS4 — 09-testing.md
+Add coverage for: AGNTCY conformance test suite (4 tests), tier enforcement tests,
+analytics service tests, and the Phase 6 test count update.
+
+### WS5 — Remaining files
+Targeted updates to: 01-overview.md (Phase 3–6 capabilities), 03-tech-stack.md (new deps),
+04-codebase-structure.md (new directories), 06-walkthroughs.md (A2A + tier + analytics flows),
+README.md (index update).