- Long-form fix: the HF pipeline's internal word-timestamp stitching crashes at
  the ~30s chunk boundary for CrisperWhisper (IndexError, dim-2 index==size). The
  service now windows manually — pipeline built without chunk_length_s; audio read
  via soundfile, split into <=28s windows (each a single Whisper pass), per-window
  word/segment timestamps offset by window start and concatenated. Verified on an
  ~11min clip: 1877 words, continuous timestamps to 673s, HTTP 200.
- Self-heal: _RemoteCrisperWhisperBackend + _RemoteNemoBackend re-ensure the
  worker and retry once on a ConnectionError, so a restarted/killed worker no
  longer leaves a stale cached service_url in acquire_stt_backend.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01R6iugoNeEgt9PkajKrFyq4