feat(governance): add V&V Architect (LeadValidator) — independent audit agent

Fixes a critical bug where VALIDATOR.md contained a copy of start-validator.sh
(making the validator unlaunchable). Introduces a fully independent V&V Architect
agent that audits the codebase against the PRD and OpenSpec outside the CTO's
chain of command.

Changes:
- VALIDATOR.md: rewritten as proper system prompt (8-phase audit methodology,
  issue format, severity model, communication protocol)
- scripts/start-validator.sh: isolated workspace setup, sanity check, auto-init
  ledger, validator-specific CLAUDE.md (no CEO context contamination)
- openspec/vv_audit/LEDGER.md: shared audit ledger index (CEO release gate view)
- openspec/changes/archive/2026-04-07-vv-architect-setup/: full OpenSpec artifacts
  (proposal.md, design.md, tasks.md — 28 tasks, all complete)

Note: .cto-workspace/CLAUDE.md updated (gitignored — persists on disk only).
#vv-findings hub channel created for real-time validator notifications.

CEO approved 2026-04-07.

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

openspec/vv_audit/LEDGER.md

@@ -0,0 +1,47 @@
+# V&V Audit Ledger
+
+**Project:** SentryAgent.ai AgentIdP
+**Maintained by:** LeadValidator (V&V Architect)
+**Ledger path:** `openspec/vv_audit/`
+
+---
+
+## Summary
+
+| Metric | Count |
+|--------|-------|
+| Total issues logged | 0 |
+| Open | 0 |
+| Resolved | 0 |
+| Disputed | 0 |
+| Last audit | — |
+| Release gate status | NOT YET AUDITED |
+
+---
+
+## Issue Index
+
+| Issue | Severity | Category | Status | Title |
+|-------|----------|----------|--------|-------|
+| — | — | — | — | No issues logged yet |
+
+<!-- LeadValidator appends a row here for every new VV_ISSUE_XXX.md logged -->
+
+---
+
+## Audit History
+
+| Date | Phases Run | Issues Found | Overall Status |
+|------|-----------|--------------|----------------|
+| — | — | — | — |
+
+<!-- LeadValidator appends a row after each completed audit session -->
+
+---
+
+## How to use this ledger
+
+- **Validator:** Update the Summary table and append to Issue Index after each session
+- **CTO:** When resolving an issue, update the issue file (VV_ISSUE_XXX.md) — do not edit this ledger directly
+- **CEO:** This ledger is your at-a-glance view of product quality gate status
+- **Release gate:** No release to production while any BLOCKER is OPEN or DISPUTED