feat(vcs): IDEA-style synchronized scrolling for the side-by-side diff (#181)

The side-by-side diff gets two independent options. Synchronize Scrolling (toolbar lock, also in the settings menu, on by default) scrolls both panes together; Align Changes (settings menu, off by default) pads the panes so changes line up. With Align Changes off, the panes keep their own heights and a divider of curved bands joins each change, with arrows to apply it; scrolling one pane moves the other through the matching change (anchored at a third of the height), including caret moves and the wheel over the divider. Scroll mapping and the divider look up changes by binary search, so large files with thousands of changes scroll smoothly.

Claude-Session: https://claude.ai/code/session_01Dq6jQQn8ZhRfkkyj3PRutA
Co-authored-by: jaw52 <[email protected]>

src/platform/locales/text/zh.json

@@ -58,6 +58,7 @@
   "Adjust colors for red-green vision deficiency": "针对红绿色觉缺陷调整颜色",
   "After Replace": "替换后",
   "After Stop, the process gets this long to exit after the interrupt before it is killed.": "停止后，进程在收到中断信号后有这么长时间退出，超时将被强制终止。",
+  "Align Changes": "对齐更改",
   "All": "全部",
   "All Places": "所有位置",
   "All breakpoints": "所有断点",