fix(anki): clarify media timing review subtitle boundaries

- Compact the timing review layout
- Label mined subtitle line start and end boundaries

src/renderer/index.html

@@ -265,9 +265,12 @@
                 </svg>
                 <div
                   class="media-timing-review-original-range"
-                  title="Original subtitle timing"
+                  title="Mined subtitle timing"
                   aria-hidden="true"
-                ></div>
+                >
+                  <span class="media-timing-review-original-boundary is-start"></span>
+                  <span class="media-timing-review-original-boundary is-end"></span>
+                </div>
                 <div
                   id="mediaTimingReviewSelectedRange"
                   class="media-timing-review-selected-range"