feat: add shallow fetch and grouped skill selection

skiff/cli.py

@@ -150,7 +150,7 @@ def _ensure_registry_fetched(name: str, entry: dict[str, object]) -> None:
         )
     _print(f"拉取外部 skill: {name}")
     subprocess.run(
-        ["git", "clone", "--branch", ref, "--", repo, str(dest)],
+        ["git", "clone", "--depth", "1", "--branch", ref, "--", repo, str(dest)],
         check=True,
     )
     if not discover_external_skills(name, entry):
@@ -563,6 +563,7 @@ def cmd_select(args: argparse.Namespace) -> None:
         expected: Path,
         kind: str,
         description: str,
+        indent: int = 0,
     ) -> SkillChoice:
         return SkillChoice(
             name=name,
@@ -579,6 +580,7 @@ def cmd_select(args: argparse.Namespace) -> None:
                 if project_root is not None
                 else ""
             ),
+            indent=indent,
         )
 
     choices = [
@@ -628,9 +630,26 @@ def cmd_select(args: argparse.Namespace) -> None:
                     expected=expected,
                     kind=f"external:{package}",
                     description=description,
+                    indent=1,
                 )
             )
             choice_requests[choice_name] = (skill_name, f"registry:{package}")
+        child_names = tuple(
+            f"{package}/{skill_name}"
+            for skill_name in skill_names
+            if f"{package}/{skill_name}" in choice_requests
+        )
+        if child_names:
+            first_child = len(choices) - len(child_names)
+            choices.insert(
+                first_child,
+                SkillChoice(
+                    name=package,
+                    kind="repository",
+                    description=str(entry.get("description", "")),
+                    children=child_names,
+                ),
+            )
 
     try:
         scope_label = (
@@ -807,7 +826,7 @@ def cmd_fetch(args: argparse.Namespace) -> None:
     else:
         _print(f"克隆: {repo} -> {dest}")
         subprocess.run(
-            ["git", "clone", "--branch", ref, "--", repo, str(dest)],
+            ["git", "clone", "--depth", "1", "--branch", ref, "--", repo, str(dest)],
             check=True,
         )