fix: add missing validation in renameAlias, add 6 tests

renameAlias was missing length (>128), reserved name, and empty string
validation that setAlias enforced. This inconsistency allowed renaming
aliases to reserved names like 'list' or 'delete'.

Also adds tests for:
- renameAlias empty string, reserved name, and length limit
- validate-skills whitespace-only SKILL.md rejection
- validate-rules whitespace-only file and recursive subdirectory scan

tests/ci/validators.test.js

@@ -470,6 +470,18 @@ function runTests() {
     cleanupTestDir(testDir);
   })) passed++; else failed++;
 
+  if (test('fails on whitespace-only SKILL.md', () => {
+    const testDir = createTestDir();
+    const skillDir = path.join(testDir, 'blank-skill');
+    fs.mkdirSync(skillDir);
+    fs.writeFileSync(path.join(skillDir, 'SKILL.md'), '   \n\t\n  ');
+
+    const result = runValidatorWithDir('validate-skills', 'SKILLS_DIR', testDir);
+    assert.strictEqual(result.code, 1, 'Should reject whitespace-only SKILL.md');
+    assert.ok(result.stderr.includes('Empty file'), 'Should report empty file');
+    cleanupTestDir(testDir);
+  })) passed++; else failed++;
+
   // ==========================================
   // validate-commands.js
   // ==========================================
@@ -673,6 +685,29 @@ function runTests() {
     cleanupTestDir(testDir);
   })) passed++; else failed++;
 
+  if (test('fails on whitespace-only rule file', () => {
+    const testDir = createTestDir();
+    fs.writeFileSync(path.join(testDir, 'blank.md'), '   \n\t\n  ');
+
+    const result = runValidatorWithDir('validate-rules', 'RULES_DIR', testDir);
+    assert.strictEqual(result.code, 1, 'Should reject whitespace-only rule file');
+    assert.ok(result.stderr.includes('Empty'), 'Should report empty file');
+    cleanupTestDir(testDir);
+  })) passed++; else failed++;
+
+  if (test('validates rules in subdirectories recursively', () => {
+    const testDir = createTestDir();
+    const subDir = path.join(testDir, 'sub');
+    fs.mkdirSync(subDir);
+    fs.writeFileSync(path.join(testDir, 'top.md'), '# Top Level Rule');
+    fs.writeFileSync(path.join(subDir, 'nested.md'), '# Nested Rule');
+
+    const result = runValidatorWithDir('validate-rules', 'RULES_DIR', testDir);
+    assert.strictEqual(result.code, 0, 'Should validate nested rules');
+    assert.ok(result.stdout.includes('Validated 2'), 'Should find both rules');
+    cleanupTestDir(testDir);
+  })) passed++; else failed++;
+
   // Summary
   console.log(`\nResults: Passed: ${passed}, Failed: ${failed}`);
   process.exit(failed > 0 ? 1 : 0);