test: cover invalid alias characters

tests/aliases.test.ts

@@ -21,11 +21,13 @@ describe('alias validation', () => {
     expect(validateAlias('   ')).toEqual({ ok: false, error: 'Alias is required' });
   });
 
-  it('rejects path separators with exact error', () => {
-    expect(validateAlias('a/b')).toEqual({
+  it('rejects invalid characters with exact error', () => {
+    for (const alias of ['a/b', 'a.b', 'a b', '中文']) {
+      expect(validateAlias(alias)).toEqual({
         ok: false,
         error: 'Alias may contain only letters, numbers, underscore, and hyphen',
       });
+    }
   });
 
   it('rejects aliases starting with hyphen or underscore', () => {