ci: add sanity test npx skills add (#29)

* fix: remove CLAUDE.md symlink generation from build

The CLAUDE.md symlink causes installation errors when using
`npx skills add` as it tries to copy AGENTS.md to itself.

- Remove createClaudeSymlink function from build.ts
- Remove claudeSymlink from SkillPaths interface
- Remove CLAUDE.md references from AGENTS.md structure documentation
- Delete existing CLAUDE.md symlink from skills directory

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* test: add sanity test for skills installation

Add a sanity test that verifies the skills CLI installation works:
- Runs `npx skills add . -a claude-code -y` using current directory
- Checks command doesn't fail (exit code 0)
- Verifies .claude/skills directory is created
- Dynamically discovers skills in the repo and verifies they're installed
- Checks SKILL.md exists in each installed skill

The test runs on every push to main and pull requests.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* Revert "fix: remove CLAUDE.md symlink generation from build"

This reverts commit c07c234601.

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -14,7 +14,7 @@ jobs:
 
       - uses: actions/setup-node@v6
         with:
-          node-version: '20'
+          node-version: "20"
 
       - name: Install dependencies
         run: npm install
@@ -30,7 +30,7 @@ jobs:
 
       - uses: actions/setup-node@v6
         with:
-          node-version: '20'
+          node-version: "20"
 
       - name: Install dependencies
         working-directory: packages/skills-build
@@ -52,3 +52,19 @@ jobs:
             git diff skills/*/AGENTS.md
             exit 1
           fi
+
+  test:
+    name: Test
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+
+      - uses: actions/setup-node@v6
+        with:
+          node-version: "20"
+
+      - name: Install dependencies
+        run: npm install
+
+      - name: Run sanity tests
+        run: npm run test:sanity