feat: integrate Pi backend and Pi Web

pi-web/app/api/cwd/browse/route.ts

@@ -0,0 +1,39 @@
+import { NextRequest, NextResponse } from "next/server";
+import { stat } from "fs/promises";
+import {
+  getBrowseStartDirectory,
+  getParentDirectory,
+  listDirectories,
+  resolveDirectory,
+} from "@/lib/directory-browser";
+
+// GET /api/cwd/browse?path=...：列出文件系统中的可读子目录。
+export async function GET(request: NextRequest) {
+  try {
+    const requested = request.nextUrl.searchParams.get("path")?.trim();
+    const candidate = getBrowseStartDirectory(requested);
+
+    let resolved: string;
+    try {
+      resolved = await resolveDirectory(candidate);
+    } catch {
+      return NextResponse.json({ error: "Directory does not exist" }, { status: 404 });
+    }
+
+
+    const directoryStat = await stat(resolved);
+    if (!directoryStat.isDirectory()) {
+      return NextResponse.json({ error: "Path is not a directory" }, { status: 400 });
+    }
+
+    const directories = await listDirectories(resolved);
+
+    return NextResponse.json({
+      path: resolved,
+      parentPath: getParentDirectory(resolved),
+      directories,
+    });
+  } catch (error) {
+    return NextResponse.json({ error: String(error) }, { status: 500 });
+  }
+}