fix(arch+design): wire architecture and design together

- Architecture route now uses /generate endpoint (no Atlas session
  overhead, no conflicting system prompt) for clean JSON generation
- Design page fetches saved architecture on load and maps designSurfaces
  to known surface IDs via fuzzy match; AI-suggested surfaces are
  pre-selected in the picker with an "AI" badge and explanatory note

Made-with: Cursor

app/api/projects/[projectId]/architecture/route.ts

@@ -137,16 +137,10 @@ ${phaseContext}
 ${prd}`;
 
   try {
-    const res = await fetch(`${AGENT_RUNNER_URL}/atlas/chat`, {
+    const res = await fetch(`${AGENT_RUNNER_URL}/generate`, {
       method: "POST",
       headers: { "Content-Type": "application/json" },
-      body: JSON.stringify({
-        message: prompt,
-        session_id: `arch_${projectId}_${Date.now()}`,
-        history: [],
-        is_init: false,
-        tools: [], // no tools needed — just structured generation
-      }),
+      body: JSON.stringify({ prompt }),
       signal: AbortSignal.timeout(120_000),
     });