feat(skill): pre-draw checkpoint, docs-sync gate, packaged self-check, ADRs

- SKILL.md: confirm type/pattern/size/cuts with the user before rendering;
  checklist hooks for the checkpoint and the packaged self-check
- scripts/verify-docs-sync.py: CI now fails when the frontmatter description
  loses a type's lexical hook, the gallery can't reach a shipped example, or
  the README tree names a missing file
- skills/diagram-design/scripts/self_check.py: distilled output checker that
  ships with the skill so installed agents can verify their own diagrams;
  adversarial suite in scripts/test-self-check.py
- assets/index.html: six new tabs (OAuth sequence + five single-variant
  examples with a data-single variant lock) so every shipped example is
  browsable
- docs/adr/0001-0004: settled policies recorded (pinned controller, taxonomy
  freeze, reveal-only autoplay, byte cap + trigger-rich description)
- README: It's-working-if section, new gates documented; CONTRIBUTING: gate
  table, ADR guidance, type-addition invariants; CI: two new steps

.github/workflows/ci.yml

@@ -104,6 +104,16 @@ jobs:
         id: motion
         run: python scripts/test-verify-motion.py
 
+      - name: Verify docs and routing sync
+        if: always()
+        id: docs_sync
+        run: python scripts/verify-docs-sync.py
+
+      - name: Verify packaged self-check
+        if: always()
+        id: self_check
+        run: python scripts/test-self-check.py
+
       - name: Verify generated icon assets
         if: always()
         id: icons
@@ -134,4 +144,6 @@ jobs:
           echo "| Draw.io Import Extractor | ${{ steps.drawio.outcome == 'success' && '✅ Passed' || (steps.drawio.outcome == 'skipped' && '⏭️ Skipped' || '❌ Failed') }} |" >> $GITHUB_STEP_SUMMARY
           echo "| Mermaid Import Extractor | ${{ steps.mermaid.outcome == 'success' && '✅ Passed' || (steps.mermaid.outcome == 'skipped' && '⏭️ Skipped' || '❌ Failed') }} |" >> $GITHUB_STEP_SUMMARY
           echo "| Optional Motion Contract | ${{ steps.motion.outcome == 'success' && '✅ Passed' || (steps.motion.outcome == 'skipped' && '⏭️ Skipped' || '❌ Failed') }} |" >> $GITHUB_STEP_SUMMARY
+          echo "| Docs & Routing Sync | ${{ steps.docs_sync.outcome == 'success' && '✅ Passed' || (steps.docs_sync.outcome == 'skipped' && '⏭️ Skipped' || '❌ Failed') }} |" >> $GITHUB_STEP_SUMMARY
+          echo "| Packaged Self-Check | ${{ steps.self_check.outcome == 'success' && '✅ Passed' || (steps.self_check.outcome == 'skipped' && '⏭️ Skipped' || '❌ Failed') }} |" >> $GITHUB_STEP_SUMMARY
           echo "| Primitive Icons & Documentation | ${{ steps.icons.outcome == 'success' && '✅ Passed' || (steps.icons.outcome == 'skipped' && '⏭️ Skipped' || '❌ Failed') }} |" >> $GITHUB_STEP_SUMMARY