style: reduce button border radius from 12px to 8px

Author: Dimillian

src/styles/main.css

@@ -288,7 +288,7 @@
   padding: 8px;
   min-width: 32px;
   min-height: 32px;
-  border-radius: 12px;
+  border-radius: 8px;
   border: 1px solid var(--cm-border-emphasis);
   background: var(--cm-surface-panel-strong);
   color: var(--text-muted);