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>

CLAUDE.md

@@ -8,7 +8,7 @@ This is a PRIVATE project session for SentryAgent.ai.
 
 ## STARTUP PROTOCOL (Required on every new session)
 On startup, Claude MUST (in order):
-1. Read `/README.md` in full before any action
+1. Read `/README.md` in full before any action — this is the project PRD (Product Requirements Document) and single source of truth
 2. Register with central hub as `CEO-Session`
 3. Check `#vpe-cto-approvals` for any pending CTO messages
 4. Identify current phase and sprint status