fix: update CI skill count to 124 and sync MCP bundle

Two CI failures since the historical-thinking domain was added:

1. validate job: hardcoded expected count was 114 — updated to 124
2. bundle-sync job: mcp-server/src/skills.json was not rebuilt after adding
   10 new skills — regenerated via `cd mcp-server && npm run bundle-skills`

registry.json also regenerated to pick up timestamp.

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

Author: GarethManning

.github/workflows/validate.yml

@@ -14,7 +14,7 @@ jobs:
         run: |
           COUNT=$(find skills/ -name "SKILL.md" | wc -l)
           echo "Skills found: $COUNT"
-          [ "$COUNT" -eq 114 ] || (echo "Expected 114 skills, found $COUNT" && exit 1)
+          [ "$COUNT" -eq 124 ] || (echo "Expected 124 skills, found $COUNT" && exit 1)
       - name: Validate YAML frontmatter
         run: python3 scripts/validate-skills.py
       - name: Validate registry.json