chore(release): prepare v0.20.0-beta.1

Trim pending change fragments, drop the breaking flag from the stats
request-safety change, and generate prerelease notes.

changes/japanese-subtitle-generation.md

@@ -1,8 +1,7 @@
 type: added
 area: subtitles
 
-- Generate local Japanese SRT subtitles with whisper.cpp from a standalone modal opened with Ctrl+Shift+G, the empty subtitle sidebar's generation button, or `subminer generate-subs`, with shared progress reporting, cancellation, safe output files, and automatic loading into the matching mpv video. The sidebar button hides while subtitle lines are loaded.
-- Configure an existing multilingual model in Settings or choose an official multilingual model, including quantized variants, in the modal or launcher. The modal shows download sizes, speed and accuracy guidance, and a recommended starting model before explicitly downloading a verified SubMiner-managed model. Executable paths are optional overrides; empty fields find whisper-cli, ffmpeg, and ffprobe on PATH. The modal's Local tools check and the launcher name any missing executable and its setting before downloading a model or extracting audio, and generation confirms the destination directory grants write and search permissions up front.
-- Optionally select Focus on spoken dialogue in the modal and use Download speech detection model to install the separate Silero model with progress and cancellation. The choice lasts for the session; a configured VAD model path sets the default. Retain uncertain audible sections so VAD rejection does not discard dialogue under music, accepting that songs may also be transcribed. Keep passages intact within Whisper's audio window, split longer passages near detected speech starts or quiet pauses with overlapping context to reduce early subtitle timing, and combine overlapping duplicate cues even when punctuation differs. Run each passage in a fresh Whisper process to prevent repeated-character output caused by state carried between files, at the cost of reloading the model per passage. Preserve original media timing and separate repeated dialogue.
-- Recommend large-v3-turbo in the model picker when NVIDIA hardware and CUDA device support in the selected Whisper executable are confirmed; recommend small otherwise. Preserve configured and session model selections. Use a wider generation modal to reduce text wrapping and scrolling, while keeping it within smaller player windows.
-- Automatically use an eligible embedded or external subtitle track loaded in mpv to guide long-passage cuts, preferring English dialogue and excluding tracks marked signs, songs, forced, or generated. Honor active subtitle delays, retain unreferenced audio, and fall back to audio timing when references cannot be read. Available in the overlay and launcher, with or without VAD. The launcher captures audio selection, reference tracks, and delays before model setup so playback changes during a download do not mix inputs from different times, and rejects an unverified media snapshot before using mpv's selected audio stream.
+- Generate Japanese SRT subtitles locally with whisper.cpp from a modal (Ctrl+Shift+G), the empty subtitle sidebar's generation button, or `subminer generate-subs`, with progress, cancellation, and automatic loading into mpv.
+- Pick an official multilingual model (including quantized variants) with size and accuracy guidance and download it in-app, or point Settings at an existing model. `large-v3-turbo` is recommended when CUDA support is detected, `small` otherwise. whisper-cli, ffmpeg, and ffprobe are found on PATH unless overridden, and missing tools are named before any download starts.
+- Optional "Focus on spoken dialogue" mode uses a separately downloadable Silero VAD model, keeping uncertain audible sections so dialogue under music is not dropped (songs may be transcribed too).
+- Long passages are split near detected speech starts or quiet pauses, guided by an eligible embedded or external subtitle track already loaded in mpv when one is available, to reduce early subtitle timing. Each passage runs in a fresh Whisper process to avoid repeated-character output.