Assistant: drop a2ui surfaces, fall back to markdown tables

CK 1.60+ validates generated a2ui ops against a component catalog before
painting, and our agent's ops fail validation — surfaces hang at
"Building interface" forever (MAF also drops RunAgentInput.context, so
the catalog/guidelines never even reach the model). Disable a2ui end to
end until the pipeline matures:

- server.ts: a2ui { enabled: false }; RENDER_TOOLS no longer includes
  render_a2ui
- App.tsx: remove the a2ui provider prop
- agent.py: prompt now asks for clean markdown tables for lists and
  structured data; render_spending_summary card guidance unchanged

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

frontend/server.ts

@@ -197,7 +197,7 @@ class StripModelArtifactsMiddleware extends (Middleware as any) {
 // below the card. This middleware buffers TEXT_MESSAGE_* events and discards
 // them if any render tool call is detected in the same turn.
 
-const RENDER_TOOLS = new Set(["render_a2ui", "render_spending_summary"]);
+const RENDER_TOOLS = new Set(["render_spending_summary"]);
 
 // eslint-disable-next-line @typescript-eslint/no-explicit-any
 class SuppressRenderToolTextMiddleware extends (Middleware as any) {
@@ -311,7 +311,10 @@ app.all("/api/copilotkit/*", async (c) => {
 
   const runtime = new CopilotRuntime({
     agents: { wealthysmart: agent },
-    a2ui: { injectA2UITool: true },
+    // a2ui disabled 2026-07-04: CK 1.60+ validates generated ops against a
+    // catalog and our agent's ops fail validation (surface never paints).
+    // Markdown tables cover the use case until the pipeline matures.
+    a2ui: { enabled: false },
     beforeRequestMiddleware: async ({ request: outbound }) => {
       if (outbound.method !== "POST") return;
       const ct = outbound.headers.get("content-type") ?? "";