MAJOR from the 2026-04-22 review (wav.rs:135-145): read_wav used
filter_map(|s| s.ok()) on both integer and float sample iterators, so
any per-sample decode error (truncated payload, corrupted format
descriptor after a partial write) was silently discarded. Callers
received Ok with a short samples vec, losing audio without any signal
to investigate.
Switches to collect::<Result<Vec<f32>>>() with a map that converts
hound's per-sample errors into KonError::AudioDecodeFailed. First
error aborts the read rather than returning a partial vector.
Test fabricates the regression by writing a valid WAV and chopping
the last 10 bytes; the previous filter_map would have returned Ok
with a shortened vec, the new code returns Err.
The Vec<f32> in-memory accumulator on run_live_session had three
failure modes: (a) a crash during transcription took the recording
with it, (b) RAM grew linearly with session length, (c) OOM killed
the capture thread silently.
New kon_audio::WavWriter wraps hound::WavWriter<BufWriter<File>> with
an append-friendly API and a 500 ms-granularity header flush. On any
abort after a flush the on-disk file is a valid, playable WAV. Unit
test (brief item #19 acceptance) simulates the abort with
std::mem::forget and asserts the pre-flush samples are recoverable.
Live capture now:
- resolves the destination path at start_live_transcription_session
time via a new resolve_recording_path helper extracted from
persist_audio_samples,
- opens a WavWriter before any samples arrive, sample rate taken from
LocalEngine::capabilities() (#13 wiring) with 16 kHz fallback,
- feeds the resampler output through WavWriter::append inside
append_resampled_audio — drops the writer with a user-visible
warning if a write fails mid-session,
- calls flush() at stop (after resampler tail), finalise() on clean
exit, and drops-to-last-flushed state on abort.
LiveSessionSummary.audio_samples → audio_path: the path is already
written by the time stop_live_transcription_session runs; no
post-session write step remains for live capture.
persist_audio_samples is kept for the offline save_audio command.
