fix(plugin): handle EXDEV cross-filesystem rename during install

fs.renameSync() fails with EXDEV when source and destination are on
different filesystem mount points. This commonly happens because plugin
clones land in os.tmpdir() (often /tmp on a tmpfs) while plugins are
installed to ~/.opencli/plugins/ (on the root filesystem).

Add a moveDir() helper that catches EXDEV and falls back to
fs.cpSync() + fs.rmSync(). Applied to both single-plugin and monorepo
install paths.

Author: ByteYue

src/plugin.ts

@@ -70,6 +70,26 @@ export interface PluginInfo {
   description?: string;
 }
 
+// ── Filesystem helpers ──────────────────────────────────────────────────────
+
+/**
+ * Move a directory, with EXDEV fallback.
+ * fs.renameSync fails when source and destination are on different
+ * filesystems (e.g. /tmp → ~/.opencli). In that case we copy then remove.
+ */
+function moveDir(src: string, dest: string): void {
+  try {
+    fs.renameSync(src, dest);
+  } catch (err: unknown) {
+    if ((err as NodeJS.ErrnoException).code === 'EXDEV') {
+      fs.cpSync(src, dest, { recursive: true });
+      fs.rmSync(src, { recursive: true, force: true });
+    } else {
+      throw err;
+    }
+  }
+}
+
 // ── Validation helpers ──────────────────────────────────────────────────────
 
 export interface ValidationResult {
@@ -266,7 +286,7 @@ function installSinglePlugin(
   }
 
   fs.mkdirSync(PLUGINS_DIR, { recursive: true });
-  fs.renameSync(cloneDir, targetDir);
+  moveDir(cloneDir, targetDir);
 
   postInstallLifecycle(targetDir);
 
@@ -298,7 +318,7 @@ function installMonorepo(
   // Move clone to permanent monorepos location (if not already there)
   if (!fs.existsSync(repoDir)) {
     fs.mkdirSync(monoreposDir, { recursive: true });
-    fs.renameSync(cloneDir, repoDir);
+    moveDir(cloneDir, repoDir);
   }
 
   let pluginsToInstall = getEnabledPlugins(manifest);