Show Qwen3 thinking output in chat as collapsible Reasoning block

Ollama streams message.thinking tokens alongside message.content when
think=True — previously silently dropped. Now forwarded end-to-end.

Backend:
- llm.py: ChatChunk type gains "thinking" variant; stream_chat_with_tools
  yields ChatChunk(type="thinking") for msg.thinking chunks before content
- generation_task.py: thinking chunks emit "thinking_chunk" SSE events
  (not added to content_so_far — not persisted to DB)

Frontend:
- types/chat.ts: Message.thinking?: string (session-only, not from DB)
- stores/chat.ts: streamingThinking ref; thinking_chunk handler accumulates
  chunks; on done, thinking carried into committed Message object then cleared
- ChatMessage.vue: collapsible <details class="thinking-block"> shown for
  messages that have .thinking content (collapsed by default)
- ChatView.vue + ChatPanel.vue: live thinking block in streaming bubble —
  open while only thinking is flowing, auto-collapses when content arrives;
  typing indicator hidden while thinking is active

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/stores/chat.ts

@@ -27,6 +27,7 @@ export const useChatStore = defineStore("chat", () => {
   const loading = ref(false);
   const streaming = ref(false);
   const streamingContent = ref("");
+  const streamingThinking = ref("");
   const streamingToolCalls = ref<ToolCallRecord[]>([]);
   const streamingStatus = ref("");
   const streamingPendingTool = ref<ToolPendingRecord | null>(null);
@@ -206,6 +207,9 @@ export const useChatStore = defineStore("chat", () => {
           case "status":
             streamingStatus.value = event.data.status as string;
             break;
+          case "thinking_chunk":
+            streamingThinking.value += event.data.chunk as string;
+            break;
           case "chunk":
             streamingContent.value += event.data.chunk as string;
             streamingStatus.value = "";
@@ -235,11 +239,13 @@ export const useChatStore = defineStore("chat", () => {
                   : null,
                 created_at: new Date().toISOString(),
                 timing: event.data.timing as GenerationTiming | undefined,
+                thinking: streamingThinking.value || undefined,
               };
               if (currentConversation.value?.id === convId) {
                 currentConversation.value.messages.push(assistantMsg);
               }
               streamingContent.value = "";
+              streamingThinking.value = "";
               streamingToolCalls.value = [];
               streamingStatus.value = "";
               streamingPendingTool.value = null;
@@ -257,6 +263,7 @@ export const useChatStore = defineStore("chat", () => {
             gotDone = true;
             streaming.value = false;
             streamingContent.value = "";
+            streamingThinking.value = "";
             streamingToolCalls.value = [];
             streamingStatus.value = "";
             streamingPendingTool.value = null;
@@ -296,6 +303,7 @@ export const useChatStore = defineStore("chat", () => {
 
     streaming.value = false;
     streamingContent.value = "";
+    streamingThinking.value = "";
     streamingToolCalls.value = [];
     streamingStatus.value = "";
     streamingPendingTool.value = null;
@@ -397,6 +405,7 @@ export const useChatStore = defineStore("chat", () => {
     loading,
     streaming,
     streamingContent,
+    streamingThinking,
     streamingToolCalls,
     streamingStatus,
     streamingPendingTool,