feat(website): add skills browse and search page to docs (#4500)

Adds a Skills Hub page to the documentation site with browsable/searchable catalog of all skills (built-in, optional, and community from cached hub indexes).

- Python extraction script (website/scripts/extract-skills.py) parses SKILL.md frontmatter and hub index caches into skills.json
- React page (website/src/pages/skills/) with search, category filtering, source filtering, and expandable skill cards
- CI workflow updated to run extraction before Docusaurus build
- Deploy trigger expanded to include skills/ and optional-skills/ changes

Authored by @IAvecilla

.github/workflows/deploy-site.yml

@@ -6,6 +6,8 @@ on:
     paths:
       - 'website/**'
       - 'landingpage/**'
+      - 'skills/**'
+      - 'optional-skills/**'
       - '.github/workflows/deploy-site.yml'
   workflow_dispatch:
 
@@ -34,6 +36,16 @@ jobs:
           cache: npm
           cache-dependency-path: website/package-lock.json
 
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.11'
+
+      - name: Install PyYAML for skill extraction
+        run: pip install pyyaml
+
+      - name: Extract skill metadata for dashboard
+        run: python3 website/scripts/extract-skills.py
+
       - name: Install dependencies
         run: npm ci
         working-directory: website