Reduce perceived latency: move context build into task, title fire-and-forget, think:False on aux calls

- build_context() moved from route handler into run_generation() background task.
  The 202 response now returns immediately; client connects to SSE before
  note search / URL fetch begins, so 'Building context...' status is visible.
- _generate_title() runs in a fire-and-forget asyncio.create_task() after the
  'done' SSE event fires. Users see their response complete 2–5s sooner on new
  conversations; title appears later in the sidebar without blocking the stream.
- generate_completion() now sets think:False and accepts a max_tokens limit.
  Intent classifier passes max_tokens=200 (JSON only), title generator passes
  max_tokens=30 (short title), eliminating qwen3 thinking-mode overhead on these
  auxiliary calls.

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

src/fabledassistant/services/generation_task.py

@@ -16,7 +16,7 @@ from fabledassistant.config import Config
 from fabledassistant.models import async_session
 from fabledassistant.models.conversation import Message
 from fabledassistant.services.generation_buffer import GenerationBuffer, GenerationState
-from fabledassistant.services.llm import ChatChunk, generate_completion, stream_chat, stream_chat_with_tools
+from fabledassistant.services.llm import ChatChunk, build_context, generate_completion, stream_chat, stream_chat_with_tools
 from fabledassistant.services.chat import update_conversation_title
 from fabledassistant.services.intent import classify_intent
 from fabledassistant.services.logging import log_generation
@@ -73,7 +73,7 @@ async def _generate_title(messages: list[dict], model: str) -> str:
         },
         {"role": "user", "content": "\n\n".join(conv_lines)},
     ]
-    title = await generate_completion(prompt_messages, model)
+    title = await generate_completion(prompt_messages, model, max_tokens=30)
     title = title.strip().strip('"\'').strip()
     return title[:100] if title else ""
 
@@ -98,18 +98,25 @@ async def _update_message(
 
 async def run_generation(
     buf: GenerationBuffer,
-    messages: list[dict],
+    history: list[dict],
     model: str,
-    context_meta: dict,
     user_id: int,
     conv_id: int,
     conv_title: str,
     user_content: str,
+    context_note_id: int | None = None,
+    exclude_note_ids: list[int] | None = None,
 ) -> None:
     """Stream LLM response into buffer with periodic DB flushes."""
     MAX_TOOL_ROUNDS = 5
     msg_id = buf.assistant_message_id
 
+    # Build context inside the background task so the 202 response returns immediately
+    buf.append_event("status", {"status": "Building context..."})
+    messages, context_meta = await build_context(
+        user_id, history, context_note_id, user_content, exclude_note_ids=exclude_note_ids
+    )
+
     # Emit context event
     buf.append_event("context", {"context": context_meta})
 
@@ -296,29 +303,6 @@ async def run_generation(
             tool_calls=all_tool_calls if all_tool_calls else None,
         )
 
-        # Count non-system messages to decide on title generation
-        non_system = [m for m in messages if m["role"] != "system"]
-        msg_count = len(non_system)
-        should_gen_title = not conv_title or (msg_count > 0 and msg_count % 10 == 0)
-
-        if should_gen_title:
-            # Include the just-generated assistant reply for context
-            title_messages = messages + [
-                {"role": "assistant", "content": buf.content_so_far}
-            ]
-            try:
-                title = await _generate_title(title_messages, model)
-                if title:
-                    await update_conversation_title(user_id, conv_id, title)
-            except Exception:
-                logger.warning("Failed to generate title for conversation %d", conv_id, exc_info=True)
-                # Fallback for first message only
-                if not conv_title:
-                    fallback = user_content[:80]
-                    if len(user_content) > 80:
-                        fallback += "..."
-                    await update_conversation_title(user_id, conv_id, fallback)
-
         timing["total_ms"] = int((time.monotonic() - t_start) * 1000)
         logger.info(
             "Generation timing for conv %d: total=%dms ttft=%s intent=%s tools=%s generation=%s",
@@ -334,6 +318,31 @@ async def run_generation(
         buf.finished_at = time.monotonic()
         buf.append_event("done", {"done": True, "message_id": msg_id, "timing": timing})
 
+        # Title generation is non-critical — fire-and-forget so done fires immediately
+        non_system = [m for m in messages if m["role"] != "system"]
+        msg_count = len(non_system)
+        should_gen_title = not conv_title or (msg_count > 0 and msg_count % 10 == 0)
+
+        if should_gen_title:
+            title_messages = messages + [
+                {"role": "assistant", "content": buf.content_so_far}
+            ]
+
+            async def _bg_title() -> None:
+                try:
+                    title = await _generate_title(title_messages, model)
+                    if title:
+                        await update_conversation_title(user_id, conv_id, title)
+                except Exception:
+                    logger.warning("Failed to generate title for conversation %d", conv_id, exc_info=True)
+                    if not conv_title:
+                        fallback = user_content[:80]
+                        if len(user_content) > 80:
+                            fallback += "..."
+                        await update_conversation_title(user_id, conv_id, fallback)
+
+            asyncio.create_task(_bg_title())
+
     except Exception as e:
         logger.exception("Error in generation task for conversation %d", conv_id)
         # Save partial content with error status