Runs the fast engine then the other from one WAV and reconciles; one engine down
uses the other and says so; the model down gives the base text unreconciled; the
cloud fallback runs only when BOTH local engines fail and is recorded as such; a
cancelled job stops everything and never reaches the cloud. The endpoint lists every
contributor. Mutation-checked, including both cancellation points.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>