feat: integrate Pi backend and Pi Web

pi-web/app/api/agent/[id]/route.ts

@@ -0,0 +1,57 @@
+import { NextResponse } from "next/server";
+import { resolveSessionPath } from "@/lib/session-reader";
+import { startRpcSession, getRpcSession } from "@/lib/rpc-manager";
+import { SessionManager } from "@earendil-works/pi-coding-agent";
+
+// POST /api/agent/[id] - Send a command to an existing session
+export async function POST(
+  req: Request,
+  { params }: { params: Promise<{ id: string }> }
+) {
+  const { id } = await params;
+
+  try {
+    const body = await req.json() as { type: string; [key: string]: unknown };
+
+    // Fast path: already-running session
+    const existing = getRpcSession(id);
+    if (existing?.isAlive()) {
+      const result = await existing.send(body);
+      return NextResponse.json({ success: true, data: result });
+    }
+
+    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 { session } = await startRpcSession(id, filePath, cwd);
+    const result = await session.send(body);
+
+    return NextResponse.json({ success: true, data: result });
+  } catch (error) {
+    return NextResponse.json({ error: String(error) }, { status: 500 });
+  }
+}
+
+// GET /api/agent/[id] - Get current agent state
+export async function GET(
+  _req: Request,
+  { params }: { params: Promise<{ id: string }> }
+) {
+  const { id } = await params;
+
+  try {
+    const session = getRpcSession(id);
+    if (!session || !session.isAlive()) {
+      return NextResponse.json({ running: false });
+    }
+
+    const state = await session.send({ type: "get_state" });
+    return NextResponse.json({ running: true, state });
+  } catch (error) {
+    return NextResponse.json({ error: String(error) }, { status: 500 });
+  }
+}