feat: integrate Pi backend and Pi Web

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

@@ -0,0 +1,31 @@
+import { NextResponse } from "next/server";
+import { SessionManager } from "@earendil-works/pi-coding-agent";
+import { resolveSessionPath, buildSessionContext } from "@/lib/session-reader";
+
+export async function GET(
+  req: Request,
+  { params }: { params: Promise<{ id: string }> }
+) {
+  const { id } = await params;
+  const url = new URL(req.url);
+  const leafId = url.searchParams.get("leafId") ?? undefined;
+  const deferThinking = url.searchParams.has("deferThinking");
+  const deferToolResultImages = url.searchParams.has("deferMedia");
+
+  try {
+    const filePath = await resolveSessionPath(id);
+    if (!filePath) {
+      return NextResponse.json({ error: "Session not found" }, { status: 404 });
+    }
+
+    const sm = SessionManager.open(filePath);
+    const context = buildSessionContext(sm.getEntries() as never, leafId, {
+      deferThinking,
+      deferToolResultImages,
+    });
+
+    return NextResponse.json({ context });
+  } catch (error) {
+    return NextResponse.json({ error: String(error) }, { status: 500 });
+  }
+}