perf(tokenizer): single-pass Yomitan scan with install-once runtime and cross-line cache

- drop the duplicate parseText full parse per line; the termsFind scanner walk
  is now authoritative and emits its own unparsed filler runs (parseText kept
  only as error fallback)
- install scan helpers once per parser window (__subminerYomitanScan) instead
  of re-shipping ~500 lines of script per subtitle line
- persist termsFind results across lines in a window-scoped LRU keyed by
  substring, invalidated via a cache epoch on dictionary/settings changes
- skip lookups at punctuation/whitespace positions and cap the shrinking-window
  retry ladder at 4 lookups per position
- build tokenizer runtime deps once (JLPT lookup cache never hit before; mecab
  availability check ran per line)
- stop restarting the prefetch run on every subtitle change; resume prefetch
  only after the tokenized payload lands, not on provisional raw emits
- add per-stage debug timings (scanMs/mecabMs/frequencyMs/annotateMs)

src/main/runtime/autoplay-subtitle-priming-runtime.test.ts

@@ -96,10 +96,10 @@ test('primeCurrentSubtitleForAutoplay refreshes active subtitle cues when mpv su
       onSubtitleChange: (text) => calls.push(`change:${text}`),
       refreshCurrentSubtitle: (text) => calls.push(`refresh:${text ?? ''}`),
     },
-    emitSubtitlePayload: (payload) => calls.push(`emit:${payload.text}`),
+    emitSubtitlePayload: (payload, options) =>
+      calls.push(`emit:${payload.text}:resume=${options?.resumePrefetch !== false}`),
     getSubtitlePrefetchService: () => ({
       pause: () => calls.push('prefetch:pause'),
-      onSeek: (timePos) => calls.push(`prefetch:seek:${timePos}`),
     }),
     getLastObservedTimePos: () => 12,
     getVisibleOverlayVisible: () => true,
@@ -120,7 +120,7 @@ test('primeCurrentSubtitleForAutoplay refreshes active subtitle cues when mpv su
     'request:time-pos',
     'set:起動字幕',
     'prefetch:pause',
-    'emit:起動字幕',
+    'emit:起動字幕:resume=false',
     'change:起動字幕',
   ]);
 });
@@ -154,10 +154,10 @@ test('primeCurrentSubtitleForAutoplay emits raw first paint on cache miss before
       onSubtitleChange: (text) => calls.push(`change:${text}`),
       refreshCurrentSubtitle: (text) => calls.push(`refresh:${text ?? ''}`),
     },
-    emitSubtitlePayload: (payload) => calls.push(`emit:${payload.text}`),
+    emitSubtitlePayload: (payload, options) =>
+      calls.push(`emit:${payload.text}:resume=${options?.resumePrefetch !== false}`),
     getSubtitlePrefetchService: () => ({
       pause: () => calls.push('prefetch:pause'),
-      onSeek: (timePos) => calls.push(`prefetch:seek:${timePos}`),
     }),
     getLastObservedTimePos: () => 12,
     getVisibleOverlayVisible: () => true,
@@ -175,7 +175,7 @@ test('primeCurrentSubtitleForAutoplay emits raw first paint on cache miss before
     'request:sub-text',
     'set:起動字幕',
     'prefetch:pause',
-    'emit:起動字幕',
+    'emit:起動字幕:resume=false',
     'change:起動字幕',
   ]);
 });