fix: quote scoped package names in skill frontmatter and update validator (#79)

- Wrapped unquoted @scope/pkg values in double quotes across 19 SKILL.md files.
- Added 'package' to ALLOWED_FIELDS in JS validator.
- Added YAML validity regression test to test suite.
- Updated package-lock.json.

Fixes #79
Closes #80

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "antigravity-awesome-skills",
-  "version": "5.2.0",
+  "version": "5.3.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "antigravity-awesome-skills",
-      "version": "5.2.0",
+      "version": "5.3.0",
       "license": "MIT",
       "bin": {
         "antigravity-awesome-skills": "bin/install.js"