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]/topic/[topicId].vue

@@ -8,7 +8,7 @@ const rootStart = Date.now();
 const chatPaneWrapper = ref<HTMLElement | null>(null);
 const inputValue = ref<BaseMessage>({ content: '', fileIds: [] });
 const route = useRoute();
-const { getAgent } = await useAgents();
+const { getAgent, deleteTopic } = await useAgents();
 const { open: sidebarOpen, openSidebar } = useSidebar();
 const { providers, allModels } = await useModels();
 const { addShortcut } = useKeyboardShortcuts();
@@ -84,12 +84,6 @@ const handleRegenerate = async (message: Message) => {
     }
 }
 
-const handleDelete = async (rootMessage: Message) => {
-    await $fetch(`/api/messages/${rootMessage.id}`, {
-        method: 'DELETE',
-    });
-}
-
 const flatMessages = computed(() => {
     const messages: Message[] = [];
 
@@ -103,6 +97,17 @@ const flatMessages = computed(() => {
     return messages;
 });
 
+const handleDelete = async (rootMessage: Message) => {
+    await $fetch(`/api/messages/${rootMessage.id}`, {
+        method: 'DELETE',
+    });
+
+    if (flatMessages.value.length === 0) {
+        await navigateTo(`/agent/${route.params.id}`);
+        deleteTopic(route.params.id as string, topicId.value);
+    }
+}
+
 const activeGeneration = computed(() => {
     if (topic.value === null) return null;
     const generations = flatMessages.value.flatMap(message => message.generation);
@@ -190,6 +195,14 @@ addShortcut(['ctrl', 'alt', 'arrowright'], async (event) => {
     }
 })
 
+addShortcut(['ctrl', 'alt', 'backspace'], async (event) => {
+    event.preventDefault();
+    event.stopPropagation();
+
+    await navigateTo(`/agent/${route.params.id}`);
+    deleteTopic(route.params.id as string, topicId.value);
+})
+
 onMounted(() => {
     scrollToBottom('instant');
 });