Background brief synthesis avoids MCP timeouts by using asynchronous task creation
with `asyncio.create_task` in the `_background_brief_synthesis` function. This
approach allows the function to run independently without blocking the main event
loop, ensuring timely responses and avoiding MCP timeouts. The synthesized brief is
saved as a markdown file in `.brain/contexts/<workspace_id>.md`.

Sources: main.py:784, main.py:1827, main.py:393, main.py:2094