feat: add GTM editor & validator skills (61, 62), update GTM audit (60)

Restructure GTM skills into audit → edit → validate workflow:
- 60-gtm-audit: MCP-based page scan, site audit, gap analysis, tag design (new code/SKILL.md)
- 61-gtm-editor: tag/trigger/variable creation via GTM API, ES5 Custom HTML, dataLayer generation
- 62-gtm-validator: QA toolkit with 7 validation modes, naming conventions, cross-platform mapping
All three skills use DTM Agent + Chrome DevTools MCP with clear handoff patterns.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

AGENTS.md

@@ -129,9 +129,19 @@ Task 2: general-purpose - "Implement the planned skill"  # Needs Task 1 result
 
 ### GTM Skills (60-69)
 
-- Use **gtm-manager** agent for GTM-specific debugging
-- Requires Chrome GTM Debug profile for live testing
-- Scripts interact with GTM API and dataLayer
+Three specialized skills with clear handoff workflow: **audit → edit → validate**
+
+| Skill | Purpose | MCP Tools |
+|-------|---------|-----------|
+| 60-gtm-audit | Scan pages, gap analysis, tag design blueprints | DTM Agent + Chrome DevTools |
+| 61-gtm-editor | Create/modify tags, triggers, variables via GTM API | DTM Agent + Chrome DevTools |
+| 62-gtm-validator | QA tag firing, trigger selectors, naming conventions | DTM Agent + Chrome DevTools |
+
+- **gtm-audit** Mode D outputs blueprints → hand off to **gtm-editor** for implementation
+- **gtm-editor** creates tags → hand off to **gtm-validator** for QA verification
+- **gtm-validator** finds broken selectors → hand back to **gtm-editor** for fixes
+- All three use DTM Agent MCP for container operations and Chrome DevTools MCP for browser inspection
+- Audit reports write to Notion GTM Audit Log database
 
 ### Jamie Clinic Skills (40-49)