Fix writing assist: disable thinking mode, drop stuck-buffer 409

- stream_chat: add think=False parameter passed through to Ollama payload.
  qwen3 models have thinking enabled by default; without this flag the model
  spends minutes generating internal thinking tokens that stream_chat silently
  discards, leaving the frontend spinner blank until the SSE connection times
  out and the widget disappears.

- create_assist_buffer: orphan (overwrite) a still-running buffer instead of
  raising. The old asyncio task holds a direct reference and completes
  harmlessly against the stale buffer. New requests always win.

- assist_route: remove the 409 guard that blocked new requests when a previous
  generation got stuck. create_assist_buffer now handles this transparently.

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

src/fabledassistant/routes/notes.py

@@ -288,11 +288,6 @@ async def assist_route():
     if not target_section or not instruction:
         return jsonify({"error": "target_section and instruction are required"}), 400
 
-    # Reject if an assist generation is already running for this user
-    existing = get_assist_buffer(uid)
-    if existing and existing.state == GenerationState.RUNNING:
-        return jsonify({"error": "Assist generation already running"}), 409
-
     model = await get_setting(uid, "default_model", Config.OLLAMA_MODEL) or Config.OLLAMA_MODEL
     messages = build_assist_messages(body, target_section, instruction)
 

src/fabledassistant/services/generation_buffer.py

@@ -100,7 +100,9 @@ def create_assist_buffer(user_id: int) -> GenerationBuffer:
     key = f"assist:{user_id}"
     existing = _buffers.get(key)
     if existing and existing.state == GenerationState.RUNNING:
-        raise RuntimeError(f"Assist generation already running for user {user_id}")
+        # Orphan the old buffer — the background task holds a direct reference
+        # and will complete against it harmlessly. A new request always wins.
+        logger.warning("Assist generation still running for user %d; orphaning old buffer", user_id)
     buf = GenerationBuffer(conversation_id=0, assistant_message_id=0)
     _buffers[key] = buf
     return buf

src/fabledassistant/services/llm.py

@@ -108,12 +108,18 @@ async def stream_chat(
     messages: list[dict],
     model: str,
     options: dict | None = None,
+    think: bool = False,
 ) -> AsyncGenerator[str, None]:
-    """Stream chat completion from Ollama, yielding content chunks."""
+    """Stream chat completion from Ollama, yielding content chunks.
+
+    Set think=False (default) to disable chain-of-thought on qwen3+ models.
+    Thinking tokens are silently discarded anyway, but disabling avoids the
+    multi-minute delay before the first content token arrives.
+    """
     merged_options = {"num_ctx": Config.OLLAMA_NUM_CTX}
     if options:
         merged_options.update(options)
-    payload: dict = {"model": model, "messages": messages, "stream": True, "options": merged_options}
+    payload: dict = {"model": model, "messages": messages, "stream": True, "options": merged_options, "think": think}
     # read=None: no per-chunk timeout — Ollama may pause for any duration while
     # processing a large input context before the first token arrives.
     async with httpx.AsyncClient(timeout=httpx.Timeout(connect=30.0, read=None, write=None, pool=30.0)) as client: