feat: add interactive skill selector

skiff/registry.py

@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+import hashlib
 from pathlib import Path
 from typing import Any
 
@@ -25,9 +26,33 @@ def save_registry(data: dict[str, dict[str, Any]], path: Path | None = None) ->
     path.write_text(yaml_io.safe_dump(data, allow_unicode=True, sort_keys=False), encoding="utf-8")
 
 
-def external_skill_path(name: str, entry: dict[str, Any] | None = None) -> Path:
+def external_repo_path(entry: dict[str, Any]) -> Path:
+    """Return the shared checkout path for a repo/ref pair."""
     from skiff.paths import EXTERNALS_DIR
 
+    repo = str(entry.get("repo", ""))
+    ref = str(entry.get("ref", "main"))
+    digest = hashlib.sha256(f"{repo}\0{ref}".encode()).hexdigest()[:16]
+    return EXTERNALS_DIR / "_repos" / digest
+
+
+def external_checkout_path(name: str, entry: dict[str, Any]) -> Path:
+    """Prefer an existing pre-shared-cache checkout for compatibility."""
+    from skiff.paths import EXTERNALS_DIR
+
+    legacy = EXTERNALS_DIR / name
+    return legacy if legacy.is_dir() else external_repo_path(entry)
+
+
+def external_skill_path(name: str, entry: dict[str, Any] | None = None) -> Path:
     entry = entry or load_registry().get(name, {})
     subpath = entry.get("path", ".") or "."
-    return (EXTERNALS_DIR / name / subpath).resolve()
+    checkout = external_checkout_path(name, entry).resolve()
+    skill_path = (checkout / subpath).resolve()
+    try:
+        skill_path.relative_to(checkout)
+    except ValueError as exc:
+        raise SystemExit(
+            f"registry 条目 {name!r} 的 path 超出外部仓库: {subpath!r}"
+        ) from exc
+    return skill_path