feat: add first-party skills, ponytail lock, and full lint suite

- add ponytail skill set to skills-lock.json (14 locked skills total)
- add first-party medusa skill under skills/, layered on install
- make test now runs ruff, shellcheck, and markdownlint-cli2
- CI installs the lint tools before make test in both workflows
- MIT license, funding buttons, thanks and donation sections in README
- .markdownlint-cli2.jsonc config; ignore lint caches in .gitignore

.github/workflows/update.yml

@@ -17,11 +17,22 @@ jobs:
       - name: ⬇️ Checkout
         uses: actions/checkout@v7
 
+      - name: 🐍 Set up Python
+        uses: actions/setup-python@v6
+        with:
+          python-version: "3.12"
+
       - name: 🔧 Set up Node.js
         uses: actions/setup-node@v6
         with:
           node-version: lts/*
 
+      - name: 📦 Install lint tools
+        run: |
+          pip install ruff
+          sudo apt-get update && sudo apt-get install -y shellcheck
+          npm install -g markdownlint-cli2
+
       - name: 🔄 Update skills
         run: make update