enhancement(#782): emit gsd skills to ~/.cline/skills for Cline >= v3.48 (#809)

Cline added a global skills system (~/.cline/skills/<name>/SKILL.md) in
v3.48.0, but gsd treated Cline as rules-only and emitted zero skills
(getGlobalSkillsBase('cline')=null, empty artifact kinds). This makes gsd
emit skills for Cline at global scope, alongside the existing .clinerules.

- runtime-homes: getGlobalSkillsBase('cline') -> ~/.cline/skills (was null)
- runtime-artifact-layout: cline emits a skills kind for GLOBAL scope only
  (local stays .clinerules-only), mirroring claude's scope dispatch
- install.js: convertClaudeCommandToClineSkill emits name+description-only
  SKILL.md frontmatter (Cline/agentskills.io spec; no Claude-specific
  allowed-tools/argument-hint/agent), hyphen-normalized + .cline/-rewritten
  body; global cline routed through the skills path while .clinerules is
  still written; _applyRuntimeRewrites cline case handles custom
  CLINE_CONFIG_DIR; convertClaudeToCliineMarkdown also rewrites bare
  ~/.claude and CLAUDE_CONFIG_DIR
- docs: install-on-your-runtime.md documents Cline global skills vs local rules
- tests: converter (name+description-only), global emission, skills+.clinerules
  coexistence, scope-aware layout, custom-dir paths, idempotency

Closes #782

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

tests/install-runtime-artifacts.test.cjs

@@ -156,14 +156,19 @@ describe('installRuntimeArtifacts — cursor commands layout (#785)', () => {
   });
 });
 
-describe('installRuntimeArtifacts — cline no-op', () => {
-  test('cline: no kinds — call succeeds, no dirs created', (t) => {
+describe('installRuntimeArtifacts — cline skills (#782)', () => {
+  test('cline: global install writes gsd-prefixed skill dirs under skills/', (t) => {
     const configDir = createTempDir('gsd-ial-cline-');
     t.after(() => cleanup(configDir));
 
     assert.doesNotThrow(() => installRuntimeArtifacts('cline', configDir, 'global', RESOLVED_CORE));
-    assert.ok(!fs.existsSync(path.join(configDir, 'skills')));
-    assert.ok(!fs.existsSync(path.join(configDir, 'commands')));
+
+    const skillsDir = path.join(configDir, 'skills');
+    assert.ok(fs.existsSync(skillsDir), 'skills/ must be created for global cline install');
+    assert.ok(
+      fs.existsSync(path.join(skillsDir, 'gsd-help', 'SKILL.md')),
+      'gsd-help/SKILL.md must exist'
+    );
   });
 });