feat: rename skills/skiff to pouch and move ACK state under .pouch

Use ~/.pouch, the pouch CLI, and .pouch.yaml as the SSOT container.
Keep the inner skills/ packages, and store ACK project state in
.pouch/ack instead of docs/ack.

tests/test_install_script.py

@@ -11,10 +11,10 @@ REPO_ROOT = Path(__file__).resolve().parents[1]
 
 
 class InstallScriptTests(unittest.TestCase):
-    def test_install_bootstraps_skiff_skill_for_all_agents(self) -> None:
+    def test_install_bootstraps_pouch_skill_for_all_agents(self) -> None:
         with tempfile.TemporaryDirectory() as temp:
             home = Path(temp)
-            (home / ".skills").symlink_to(REPO_ROOT, target_is_directory=True)
+            (home / ".pouch").symlink_to(REPO_ROOT, target_is_directory=True)
             env = os.environ.copy()
             env["HOME"] = str(home)
 
@@ -29,15 +29,15 @@ class InstallScriptTests(unittest.TestCase):
 
             self.assertEqual(result.returncode, 0, result.stderr)
             for relative in (
-                ".cursor/skills/skiff",
-                ".claude/skills/skiff",
-                ".codex/skills/skiff",
-                ".agents/skills/skiff",
+                ".cursor/skills/pouch",
+                ".claude/skills/pouch",
+                ".codex/skills/pouch",
+                ".agents/skills/pouch",
             ):
                 link = home / relative
                 self.assertTrue(link.is_symlink(), relative)
-                self.assertEqual(link.resolve(), (REPO_ROOT / "skills" / "skiff").resolve())
-            self.assertIn("已全局安装 builtin skiff skill", result.stdout)
+                self.assertEqual(link.resolve(), (REPO_ROOT / "skills" / "pouch").resolve())
+            self.assertIn("已全局安装 builtin pouch skill", result.stdout)
 
 
 if __name__ == "__main__":