feat: update GTM skills triad with field-tested improvements

gtm-audit (60):
- Added Mode D rule: check elements for IDs before designing CSS triggers

gtm-editor (61):
- Added "Tagging Workflow: dataLayer First" section — always suggest
  dataLayer push code for developers before creating GTM triggers
- Added multi-language snippets (JS, React, Vue, PHP)
- Added "Trigger Design: IDs First" section — prefer element IDs,
  ask user to add IDs before falling back to CSS selectors
- Added ID naming convention: [section]-[element]-[action]
- Added decision tree for trigger selection

gtm-validator (62):
- Flag CSS-based triggers as fragility risk during QA
- Recommend adding IDs instead of finding alternative CSS selectors

Based on field testing with ourdigital.org GTM-N9TPJW container.

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

custom-skills/60-gtm-audit/code/SKILL.md

@@ -136,5 +136,6 @@ One GA4 page_view fires to multiple endpoints — this is normal:
 - Wait for page to fully load before capturing network requests
 - Use `evaluate_script` to check consent mode before interpreting missing tags
 - Orphan count may be high due to GA4 multi-endpoint — note this in reports
+- **In Mode D (tag design), check elements for `id` attributes** — if missing, recommend adding IDs before designing CSS-based triggers. Suggest naming: `[section]-[element]-[action]`
 - Hand off tag creation work to `gtm-editor` skill
 - Hand off QA/validation work to `gtm-validator` skill