fix(app): highlight selected change

Track clicked file in the Changes tree and apply selection styling to the matching review diff.

packages/ui/src/components/button.css

@@ -43,6 +43,10 @@
     background-color: transparent;
     color: var(--text-strong);
 
+    [data-slot="icon-svg"] {
+      color: var(--icon-base);
+    }
+
     &:hover:not(:disabled) {
       background-color: var(--surface-raised-base-hover);
     }
@@ -54,8 +58,11 @@
     }
     &:disabled {
       color: var(--text-weak);
-      opacity: 0.7;
       cursor: not-allowed;
+
+      [data-slot="icon-svg"] {
+        color: var(--icon-disabled);
+      }
     }
     &[data-selected="true"]:not(:disabled) {
       background-color: var(--surface-raised-base-hover);