Fix importer hang when transcription fails
sense.py now emits observe.observed with error info when handlers fail,
instead of silently abandoning the segment. The importer polling loop
handles these errors gracefully (partial success) and includes a 10-minute
timeout as a safety net. Failed segments are persisted to imported.json.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>