feat: separate frontend and backend services

pi-web/next.config.ts

@@ -5,7 +5,7 @@ import { join } from "path";
 const { version } = JSON.parse(readFileSync(join(__dirname, "package.json"), "utf8")) as { version: string };
 let piVersion = "unknown";
 try {
-  const piPkgPath = join(__dirname, "node_modules/@earendil-works/pi-coding-agent/package.json");
+  const piPkgPath = join(__dirname, "..", "server", "node_modules", "@earendil-works", "pi-coding-agent", "package.json");
   piVersion = (JSON.parse(readFileSync(piPkgPath, "utf8")) as { version: string }).version;
 } catch { /* package not found, use default */ }
 
@@ -14,16 +14,28 @@ const allowedDevOrigins = [
   ...(process.env.PI_WEB_ALLOWED_HOSTS?.split(",") ?? []),
 ].map((origin) => origin.trim()).filter(Boolean);
 
+// All /api routes are served by the standalone backend (pi-agent-server) so
+// agent sessions and server state survive frontend recompiles and restarts.
+const serverOrigin = `http://127.0.0.1:${process.env.PI_SERVER_PORT ?? "30142"}`;
+
 const nextConfig: NextConfig = {
   devIndicators: false,
-  serverExternalPackages: [
-    "undici",
-    "@earendil-works/pi-coding-agent",
-    "@earendil-works/pi-agent-core",
-    "@earendil-works/pi-ai",
-    "@earendil-works/pi-tui",
-  ],
   allowedDevOrigins,
+  async rewrites() {
+    // beforeFiles is required: default (afterFiles) rewrites lose to the
+    // existing app/api route handlers in dev, so the migrated routes
+    // would keep hitting the local copies instead of the backend.
+    return {
+      beforeFiles: [
+        {
+          source: "/api/:path*",
+          destination: `${serverOrigin}/api/:path*`,
+        },
+      ],
+      afterFiles: [],
+      fallback: [],
+    };
+  },
   async headers() {
     return [
       {