fix: improve chat flow and cleanup

Awaits sendMessage before navigating to prevent race conditions. Passes
agentId to startGeneration for correct agent resolution. Adds topic
deletion via Ctrl+Alt+Backspace shortcut. Adds date/time prefix to user
messages in LLM context. Fixes reasoning-container typo.

app/pages/agent/[id]/index.vue

@@ -55,25 +55,26 @@ const handleSubmit = async (message: BaseMessage, model: ModelWithProvider | nul
 
     const { sendMessage, startGeneration } = await useChat(topic.id, false);
 
-    sendMessage(message).then(async res => {
-        if (res.ok === false) {
-            console.error('Failed to send message:', res.error);
+    const res = await sendMessage(message);
+    if (res.ok === false) {
+        console.error('Failed to send message:', res.error);
 
-            pendingMessage.value = null;
+        pendingMessage.value = null;
 
-            await navigateTo(`/agent/${route.params.id}`);
+        await navigateTo(`/agent/${route.params.id}`);
 
-            nextTick(() => {
-                inputValue.value = message;
-            });
-        }
-    });
+        nextTick(() => {
+            inputValue.value = message;
+        });
+
+        return;
+    }
 
     await navigateTo(`/agent/${route.params.id}/topic/${topic.id}`);
 
     autoRenameTopic(topic.id);
 
-    return startGeneration(model);
+    return startGeneration(model, undefined, route.params.id as string);
 };
 </script>