feat(ui): implement explicit chat modes for collaborate, delegate, and vibe coding

vibn-frontend/components/vibn-chat/chat-panel.tsx

@@ -788,6 +788,7 @@ export function ChatPanel({
   const [activeThread, setActiveThread] = useState<string | null>(null);
   const [messages, setMessages] = useState<Message[]>([]);
     const [input, setInput] = useState("");
+  const [chatMode, setChatMode] = useState<"collaborate" | "vibe" | "delegate">("collaborate");
   const [sending, setSending] = useState(false);
   const [showThreads, setShowThreads] = useState(false);
   const [mcpToken, setMcpToken] = useState<string | null>(null);
@@ -1029,6 +1030,33 @@ export function ChatPanel({
       abortRef.current = controller;
 
       try {
+        // If Delegate mode is selected, route to the background runner instead of streaming chat!
+        if (chatMode === "delegate") {
+          const r = await fetch(
+            `/api/projects/${projectId}/agent/sessions`,
+            {
+              method: "POST",
+              headers: { "Content-Type": "application/json" },
+              body: JSON.stringify({
+                appName: "frontend",
+                appPath: ".",
+                task: text,
+              }),
+            },
+          );
+          if (!r.ok) {
+            const err = await r.json().catch(() => ({}));
+            throw new Error(err.error || `HTTP ${r.status}`);
+          }
+          
+          setMessages((prev) => [
+            ...prev,
+            { role: "assistant", content: "I have started a background runner for this task. You can safely close this browser or work on something else. I will commit and ship the code when I am finished!" },
+          ]);
+          setSending(false);
+          return;
+        }
+
         const res = await fetch("/api/chat", {
           method: "POST",
           headers: { "Content-Type": "application/json" },
@@ -1037,6 +1065,7 @@ export function ChatPanel({
             message: text,
             workspace,
             mcp_token: mcpToken,
+            chatMode,
           }),
           signal: controller.signal,
         });