The browser extension's apiFetch treats any 404 as a missing endpoint and
retries the legacy non-/api/lm URL, producing two spurious
'error_middleware - WARNING - API GET ... 404' log lines per occurrence.
- complete_download_in_queue / update_download_queue_status /
retry_download_from_history: 'not found' is a normal business outcome,
return 200 + success:false instead of 404 (extension behavior unchanged;
apiGet ignores the HTTP status)
- error_middleware: downgrade /api/lm/download-progress/ 404s to debug like
previews - the 404 status itself stays (extension uses it for failure
detection), only the log level is lowered
Will Miao