Enable thinking mode in full chat view, keep disabled in widget/panel

stream_chat_with_tools now accepts a think parameter. run_generation
forwards it to Ollama. The message POST route reads think from the
request body. ChatView passes think=true so qwen3 uses chain-of-thought
reasoning for full conversations; the dashboard widget and ChatPanel
omit it, staying fast. Dashboard button updated to "Think it through
in Chat →" to signal the deeper capability.

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

src/fabledassistant/routes/chat.py

@@ -106,6 +106,7 @@ async def send_message_route(conv_id: int):
         return jsonify({"error": "content is required"}), 400
     context_note_id = data.get("context_note_id")
     exclude_note_ids = data.get("exclude_note_ids") or []
+    think = bool(data.get("think", False))
 
     # Reject if generation already running for this conversation
     existing = get_buffer(conv_id)
@@ -134,6 +135,7 @@ async def send_message_route(conv_id: int):
         uid, conv_id, conv.title, content,
         context_note_id=context_note_id,
         exclude_note_ids=exclude_note_ids,
+        think=think,
     ))
 
     return jsonify({