fix(security): restrict skill download target paths

src/infra/install-safe-path.ts

@@ -1,3 +1,4 @@
+import { createHash } from "node:crypto";
 import path from "node:path";
 
 export function unscopedPackageName(name: string): string {
@@ -16,6 +17,30 @@ export function safeDirName(input: string): string {
   return trimmed.replaceAll("/", "__").replaceAll("\\", "__");
 }
 
+export function safePathSegmentHashed(input: string): string {
+  const trimmed = input.trim();
+  const base = trimmed
+    .replaceAll(/[\\/]/g, "-")
+    .replaceAll(/[^a-zA-Z0-9._-]/g, "-")
+    .replaceAll(/-+/g, "-")
+    .replaceAll(/^-+/g, "")
+    .replaceAll(/-+$/g, "");
+
+  const normalized = base.length > 0 ? base : "skill";
+  const safe = normalized === "." || normalized === ".." ? "skill" : normalized;
+
+  const hash = createHash("sha256").update(trimmed).digest("hex").slice(0, 10);
+
+  if (safe !== trimmed) {
+    const prefix = safe.length > 50 ? safe.slice(0, 50) : safe;
+    return `${prefix}-${hash}`;
+  }
+  if (safe.length > 60) {
+    return `${safe.slice(0, 50)}-${hash}`;
+  }
+  return safe;
+}
+
 export function resolveSafeInstallDir(params: {
   baseDir: string;
   id: string;