feat: add Atlas discovery chat UI and API route

- components/AtlasChat.tsx — conversational PRD discovery UI (violet theme)
- app/api/projects/[projectId]/atlas-chat/route.ts — proxy + DB persistence
- overview/page.tsx — show Atlas for new projects, Orchestrator once PRD done

Made-with: Cursor

app/[workspace]/project/[projectId]/overview/page.tsx

@@ -13,6 +13,7 @@ import {
 import { Button } from "@/components/ui/button";
 import { Badge } from "@/components/ui/badge";
 import { OrchestratorChat } from "@/components/OrchestratorChat";
+import { AtlasChat } from "@/components/AtlasChat";
 import {
   GitBranch,
   GitCommit,
@@ -78,6 +79,9 @@ interface Project {
   deploymentUrl?: string;
   // Theia
   theiaWorkspaceUrl?: string;
+  // Stage
+  stage?: 'discovery' | 'architecture' | 'building' | 'active';
+  prd?: string;
   // Context
   contextSnapshot?: ContextSnapshot;
   stats?: { sessions: number; costs: number };
@@ -199,11 +203,18 @@ export default function ProjectOverviewPage() {
   return (
     <div className="container mx-auto py-8 px-6 max-w-5xl space-y-6">
 
-      {/* ── Orchestrator Chat ── */}
-      <OrchestratorChat
-        projectId={projectId}
-        projectName={project.productName}
-      />
+      {/* ── Agent Panel — Atlas for discovery, Orchestrator once PRD is done ── */}
+      {(!project.stage || project.stage === 'discovery') ? (
+        <AtlasChat
+          projectId={projectId}
+          projectName={project.productName}
+        />
+      ) : (
+        <OrchestratorChat
+          projectId={projectId}
+          projectName={project.productName}
+        />
+      )}
 
       {/* ── Header ── */}
       <div className="flex items-start justify-between">