feat: integrate Pi backend and Pi Web

pi-web/app/api/sessions/[id]/auto-name/route.ts

@@ -0,0 +1,46 @@
+import { NextResponse } from "next/server";
+import { SessionManager, type AgentSession } from "@earendil-works/pi-coding-agent";
+import { generateSessionTitle } from "@/lib/session-title";
+import { getRpcSession, startRpcSession } from "@/lib/rpc-manager";
+import { invalidateSessionListCache, resolveSessionPath } from "@/lib/session-reader";
+
+export async function POST(
+  _req: Request,
+  { params }: { params: Promise<{ id: string }> },
+) {
+  const { id } = await params;
+
+  try {
+    const filePath = await resolveSessionPath(id);
+    if (!filePath) {
+      return NextResponse.json({ error: "Session not found" }, { status: 404 });
+    }
+
+    const cwd = SessionManager.open(filePath).getHeader()?.cwd ?? process.cwd();
+    const existing = getRpcSession(id);
+    const { session } = existing?.isAlive()
+      ? { session: existing }
+      : await startRpcSession(id, filePath, cwd);
+
+    // globalThis keeps wrappers alive across dev hot reloads; older instances
+    // may predate waitUntilReady(), but those have already completed startup.
+    await session.waitUntilReady?.();
+    const result = await generateSessionTitle(session.inner as unknown as AgentSession);
+
+    if (!session.isAlive()) {
+      return NextResponse.json(
+        { error: "The session was closed while its title was being generated. Please try again." },
+        { status: 409 },
+      );
+    }
+
+    session.inner.setSessionName(result.title);
+    invalidateSessionListCache();
+    return NextResponse.json({ title: result.title, usage: result.usage ?? null });
+  } catch (error) {
+    return NextResponse.json(
+      { error: error instanceof Error ? error.message : String(error) },
+      { status: 500 },
+    );
+  }
+}