Fix line-button issue after file selection in file tree (#34574)

Fix the issue where the line-button fails to work after selecting a file
from the file tree.

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Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

web_src/css/repo/file-view.css

@@ -1,7 +1,10 @@
-.file-view tr.active {
+.file-view tr.active .lines-num,
+.file-view tr.active .lines-escape,
+.file-view tr.active .lines-code {
   background: var(--color-highlight-bg);
 }
 
+/* set correct border radius on the last active lines, to avoid border overflow */
 .file-view tr.active:last-of-type .lines-code {
   border-bottom-right-radius: var(--border-radius);
 }
@@ -10,6 +13,7 @@
   position: relative;
 }
 
+/* add a darker "handler" at the beginning of the active line */
 .file-view tr.active .lines-num::before {
   content: "";
   position: absolute;