feat(jimaku): auto-open modal when a video has no Japanese subtitle (#319)

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
Co-authored-by: Ivan Melck <ivan@spec-kitty.ai>

changes/jimaku-auto-open-missing-subtitle.md

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+type: added
+area: jimaku
+
+- Added `jimaku.autoOpenWhenPrimarySubtitleMissing` (off by default). When a local video loads without a Japanese (primary-language) subtitle track, SubMiner pauses playback and opens the Jimaku modal; playback resumes when the modal closes.
+- Opening Jimaku while it is already open now reloads the title and episode if the video changed, instead of keeping the previous episode's search.