✨ feat(skills): add skill_link symlink support + platform-agnostic prompt

- Add skill_link config option to create a symlink/junction from another
  platform's skills dir to agents_home/skills/ (e.g. ~/.claude -> ~/.agents)
- On Windows, falls back to directory junction when symlink requires admin
- Add _create_skills_symlink() with _is_junction() helper for Windows
- Update playbook.toml.example with skill_link documentation
- Fix templates/README.md prompt example to be platform-agnostic
- Add 3 tests: symlink creation, idempotency, absence when unconfigured

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/cli/test_playbook_cli.py

@@ -583,5 +583,86 @@ project_name = "Demo"
             self.assertEqual(claude_md.read_text(encoding="utf-8"), original)
 
 
+    def test_install_skills_creates_symlink_when_skill_link_configured(self):
+        with tempfile.TemporaryDirectory() as tmp_dir:
+            root = Path(tmp_dir)
+            agents_home = root / "agents"
+            link_home = root / "claude"
+            config_body = f"""
+[playbook]
+project_root = "{tmp_dir}"
+deploy_root = "{CUSTOM_DEPLOY_ROOT}"
+
+[install_skills]
+agents_home = "{agents_home}"
+skill_link = "{link_home}"
+mode = "list"
+skills = ["commit-message"]
+"""
+            config_path = root / "playbook.toml"
+            config_path.write_text(config_body, encoding="utf-8")
+
+            result = run_cli("-config", str(config_path))
+
+            self.assertEqual(result.returncode, 0, msg=result.stdout + result.stderr)
+            skills_dst = agents_home / "skills"
+            link_path = link_home / "skills"
+            self.assertTrue(skills_dst.is_dir())
+            self.assertTrue(link_path.is_dir(), "link_path should be accessible as dir")
+            self.assertEqual(link_path.resolve(), skills_dst.resolve())
+            self.assertTrue((link_path / "commit-message" / "SKILL.md").is_file())
+
+    def test_install_skills_symlink_is_idempotent(self):
+        with tempfile.TemporaryDirectory() as tmp_dir:
+            root = Path(tmp_dir)
+            agents_home = root / "agents"
+            link_home = root / "claude"
+            config_body = f"""
+[playbook]
+project_root = "{tmp_dir}"
+deploy_root = "{CUSTOM_DEPLOY_ROOT}"
+
+[install_skills]
+agents_home = "{agents_home}"
+skill_link = "{link_home}"
+mode = "list"
+skills = ["commit-message"]
+no_backup = true
+"""
+            config_path = root / "playbook.toml"
+            config_path.write_text(config_body, encoding="utf-8")
+
+            run_cli("-config", str(config_path))
+            result = run_cli("-config", str(config_path))
+
+            self.assertEqual(result.returncode, 0, msg=result.stdout + result.stderr)
+            self.assertTrue((link_home / "skills").is_dir())
+
+    def test_install_skills_no_symlink_when_skill_link_absent(self):
+        with tempfile.TemporaryDirectory() as tmp_dir:
+            root = Path(tmp_dir)
+            agents_home = root / "agents"
+            config_body = f"""
+[playbook]
+project_root = "{tmp_dir}"
+deploy_root = "{CUSTOM_DEPLOY_ROOT}"
+
+[install_skills]
+agents_home = "{agents_home}"
+mode = "list"
+skills = ["commit-message"]
+"""
+            config_path = root / "playbook.toml"
+            config_path.write_text(config_body, encoding="utf-8")
+
+            result = run_cli("-config", str(config_path))
+
+            self.assertEqual(result.returncode, 0, msg=result.stdout + result.stderr)
+            self.assertFalse(any(
+                p.is_symlink() for p in (agents_home / "skills").iterdir()
+                if p.is_symlink()
+            ) if (agents_home / "skills").exists() else False)
+
+
 if __name__ == "__main__":
     unittest.main()