Streams the WAV from disk with a computed Content-Length (no buffering, no
chunking), posts verbose_json with field `file` and language=sv, clamps the
final segment to the audio duration, and treats an empty transcript as a
failure. The chain falls back on ANY primary error, records the serving
endpoint, and never falls back once the context is cancelled.
gateway.go and chain.go are one commit: the chain's tests use the gateway's
StatusError and ErrEmptyTranscript, so neither compiles alone.
Mutation-checked: field name, clamp, cancel-fallback, content length and the
recorded endpoint each turn a test red.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
