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

skills-lock.json

@@ -48,6 +48,42 @@
       "sourceType": "github",
       "skillPath": "skills/compress/SKILL.md",
       "computedHash": "c91bdf427a68b686ee9d6f63766c72d164b16915434736edfedf13e24dae0e8c"
+    },
+    "ponytail": {
+      "source": "DietrichGebert/ponytail",
+      "sourceType": "github",
+      "skillPath": "skills/ponytail/SKILL.md",
+      "computedHash": "210fa0831f649ce9f8a305f7b7c8cf2a0dd09ac4dd53067109941b96e7811d4e"
+    },
+    "ponytail-audit": {
+      "source": "DietrichGebert/ponytail",
+      "sourceType": "github",
+      "skillPath": "skills/ponytail-audit/SKILL.md",
+      "computedHash": "8b8d72e6ff70b65b6c9518d470fcf29dc696eea93d28f3efa10fdcc60cbd696d"
+    },
+    "ponytail-debt": {
+      "source": "DietrichGebert/ponytail",
+      "sourceType": "github",
+      "skillPath": "skills/ponytail-debt/SKILL.md",
+      "computedHash": "0099b82174e3a4261828b4ec04d2c068b1b294fdab14f76701c2acd1f7c99539"
+    },
+    "ponytail-gain": {
+      "source": "DietrichGebert/ponytail",
+      "sourceType": "github",
+      "skillPath": "skills/ponytail-gain/SKILL.md",
+      "computedHash": "c45ecba7906960eea904218b623abf097ebff84ecbacca6d68da1d0687435f75"
+    },
+    "ponytail-help": {
+      "source": "DietrichGebert/ponytail",
+      "sourceType": "github",
+      "skillPath": "skills/ponytail-help/SKILL.md",
+      "computedHash": "10e8382b1033c9a0fec0073de6d3de3846b4f5dca7d78b6df2d476a1f4cd43c6"
+    },
+    "ponytail-review": {
+      "source": "DietrichGebert/ponytail",
+      "sourceType": "github",
+      "skillPath": "skills/ponytail-review/SKILL.md",
+      "computedHash": "4646594fcd75455533f7ff1425f4f1c5ba0fa65f88241bf262b1c4fc275f049a"
     }
   }
 }