feat(youtube): add YouTube browser window and Whisper subtitle source

- Add `subminer youtube`/`yt` and tray "Browse YouTube" window that plays or queues picked videos in mpv
- Add `youtube.subtitleSource` (`youtube` | `whisper`) to transcribe YouTube audio via subtitle generation
- Allow the subtitle generation modal on YouTube videos
- Pick the real Japanese track over machine-translated ones and fall back to yt-dlp on HTTP 429
- Remove legacy launcher youtubeSubgen/whisper/AI args and `--youtube-mode`
- Fix EPIPE crash when the launching terminal is closed with Ctrl+C
- Thin media timing review handles with orange original-boundary bars
- Update docs and change fragments

src/renderer/index.html

@@ -393,12 +393,6 @@
                   <span class="media-timing-review-original-boundary is-start"></span>
                   <span class="media-timing-review-original-boundary is-end"></span>
                 </div>
-                <span class="media-timing-review-original-label is-start" aria-hidden="true">
-                  Line start
-                </span>
-                <span class="media-timing-review-original-label is-end" aria-hidden="true">
-                  Line end
-                </span>
                 <div
                   id="mediaTimingReviewSelectedRange"
                   class="media-timing-review-selected-range"

src/renderer/modals/media-timing-review.ts

@@ -449,8 +449,8 @@ export function createMediaTimingReviewModal(
   }
 
   /**
-   * Moves an untouched clip end back to where the line's dialogue ends. The Line end
-   * rail keeps marking the subtitle timing, and Reset restores it.
+   * Moves an untouched clip end back to where the line's dialogue ends. The orange
+   * end bar keeps marking the subtitle timing, and Reset restores it.
    */
   function trimTrailingSilence(peaks: readonly number[]): void {
     if (!payload || !trailingTrimPending || previewPlaying || previewRequest.isInFlight()) {

src/renderer/modals/subtitle-generation.ts

@@ -88,7 +88,7 @@ export function createSubtitleGenerationModal(
     const vad = snapshot ? describeGenerationVad(snapshot.vad) : null;
     const tools = snapshot ? describeGenerationTools(snapshot.tools) : null;
     const readyMessage = !snapshot?.mediaPath
-      ? 'Open local media to generate subtitles.'
+      ? 'Open a local file or a YouTube video to generate subtitles.'
       : !tools?.ready
         ? 'Install the missing tools or set their paths in Settings, then click Check again.'
         : !model?.ready
@@ -96,7 +96,8 @@ export function createSubtitleGenerationModal(
           : !vad?.ready
             ? 'Download the speech detection model or uncheck Focus on spoken dialogue.'
             : 'Ready when you are.';
-    dom.media.textContent = snapshot?.mediaPath ?? 'Open a local media file in the player first.';
+    dom.media.textContent =
+      snapshot?.mediaPath ?? 'Open a local file or a YouTube video in the player first.';
     dom.tools.textContent = tools?.text ?? 'Checking local tools...';
     dom.model.textContent = model?.text ?? 'Checking local models...';
     dom.modelPicker.classList.toggle('hidden', !snapshot || Boolean(snapshot.externalModelPath));

src/renderer/style.css

@@ -1763,34 +1763,6 @@ body:focus-visible,
   right: 0;
 }
 
-.media-timing-review-original-label {
-  position: absolute;
-  z-index: 7;
-  padding: 3px 5px;
-  border: 1px solid color-mix(in srgb, var(--ctp-crust) 35%, transparent);
-  border-radius: 4px;
-  background: var(--ctp-peach);
-  box-shadow: 0 2px 6px color-mix(in srgb, var(--ctp-crust) 55%, transparent);
-  color: var(--ctp-crust);
-  font-size: 8px;
-  font-weight: 800;
-  letter-spacing: 0.06em;
-  line-height: 1;
-  pointer-events: none;
-  white-space: nowrap;
-  text-transform: uppercase;
-}
-
-.media-timing-review-original-label.is-start {
-  top: 5px;
-  left: calc(var(--original-start) + 7px);
-}
-
-.media-timing-review-original-label.is-end {
-  right: calc(100% - var(--original-end) + 7px);
-  bottom: 5px;
-}
-
 .media-timing-review-track.is-loading::after {
   position: absolute;
   z-index: 2;
@@ -1856,61 +1828,62 @@ body:focus-visible,
   }
 }
 
+/* A thin line centered on the clip edge, so the line itself is the trim boundary. */
 .media-timing-review-handle {
   position: absolute;
   z-index: 6;
   top: 0;
   bottom: 0;
-  width: 14px;
-  border: 1px solid var(--ctp-teal);
-  background: linear-gradient(
-    180deg,
-    var(--ctp-teal),
-    color-mix(in srgb, var(--ctp-teal) 74%, var(--ctp-crust))
-  );
+  width: 3px;
+  background: var(--ctp-teal);
   cursor: ew-resize;
   touch-action: none;
+  transform: translateX(-50%);
   transition: box-shadow 130ms ease;
 }
 
-/* Widens the grab area past the visible bracket without moving the clip edge. */
+/* Widens the grab area past the visible line without moving the clip edge. */
 .media-timing-review-handle::before {
   position: absolute;
-  inset: 0 -7px;
+  inset: 0 -8px;
   content: '';
 }
 
+/* Grip knob, symmetric about the line so it never reads as a separate edge. */
 .media-timing-review-handle::after {
   position: absolute;
   top: 50%;
   left: 50%;
-  width: 6px;
-  height: 18px;
+  width: 7px;
+  height: 16px;
   content: '';
-  border-inline: 1px solid color-mix(in srgb, var(--ctp-crust) 55%, transparent);
+  border: 1px solid color-mix(in srgb, var(--ctp-crust) 55%, transparent);
+  border-radius: 4px;
+  background: var(--ctp-teal);
   transform: translate(-50%, -50%);
+  pointer-events: none;
 }
 
 .media-timing-review-handle-start {
   left: var(--selection-start);
-  border-radius: 5px 0 0 5px;
 }
 
 .media-timing-review-handle-end {
   left: var(--selection-end);
-  border-radius: 0 5px 5px 0;
-  transform: translateX(-100%);
 }
 
 .media-timing-review-handle:hover {
-  box-shadow: 0 0 16px color-mix(in srgb, var(--ctp-teal) 60%, transparent);
+  box-shadow: 0 0 10px color-mix(in srgb, var(--ctp-teal) 70%, transparent);
 }
 
 .media-timing-review-handle:focus-visible {
   outline: 2px solid transparent;
-  box-shadow:
-    inset 0 0 0 2px var(--ctp-yellow),
-    0 0 16px color-mix(in srgb, var(--ctp-yellow) 55%, transparent);
+  background: var(--ctp-yellow);
+  box-shadow: 0 0 12px color-mix(in srgb, var(--ctp-yellow) 60%, transparent);
+}
+
+.media-timing-review-handle:focus-visible::after {
+  background: var(--ctp-yellow);
 }
 
 .media-timing-review-expand-row span {