fix(subtitles): retain uncertain audio during dialogue generation

- Preserve audio rejected by VAD so dialogue under music is retained.
- Keep short passages intact and stitch overlapping cues despite punctuation differences.

changes/japanese-subtitle-generation-docs.md

@@ -0,0 +1,4 @@
+type: docs
+area: subtitles
+
+- Explain how dialogue generation retains uncertain audible sections, why songs may also be transcribed, and how passage boundaries affect subtitles.

changes/japanese-subtitle-generation.md

@@ -3,4 +3,4 @@ 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. With the detector executable installed, retain brief utterances and extra audio around speech, split long passages near quiet pauses with overlapping context, and combine duplicate cues by greatest timing overlap. Keep original media timing and separate repeated dialogue without spanning omitted music breaks.
+- 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 quiet pauses with overlapping context, and combine overlapping duplicate cues even when punctuation differs. Preserve original media timing and separate repeated dialogue.