fix(svelte): Better preloading in file tree (#64327)

Currently the link element doesn't extend to the full width of the
sidebar. You can click outside of the actual text to navigate to the
file, but it won't be preloaded.

Now the link occupies the full width.

## Test plan

Manual testing.

client/web-sveltekit/src/lib/TreeNode.svelte

@@ -175,6 +175,7 @@
                 display: inherit;
                 gap: inherit;
                 margin-left: var(--indent-size);
+                width: 100%;
             }
         }
 

client/web-sveltekit/src/routes/[...repo=reporev]/(validrev)/(code)/FileTree.svelte

@@ -185,8 +185,6 @@
     }
 
     a {
-        text-overflow: ellipsis;
-        overflow: hidden;
         white-space: nowrap;
         color: inherit;
         text-decoration: none;