chore: various UI problems (#38263)

1. fix dirty "list" styles for "githooks" and "webhooks"
2. fix git hook edit page layout
3. fix codemirror editor styles
4. fix incorrect "ui attached header" width

web_src/css/repo/file-view.css

@@ -1,7 +1,5 @@
 .file-view-container {
   padding: 0 !important; /* the file-view itself provides padding */
-  width: 100% !important; /* override fomantic's "100% + 2px" */
-  max-width: 100% !important;
 }
 
 .file-view tr.active .lines-num,