fix(maestro): apply tool-arg truncation fix to styles.css duplicate

The previous fix (e3556bd) added `flex: 1 1 0` to `.st-tool-arg` in
`structured.css`, but `styles.css` has a duplicate copy of the same
rules that was left stale. Because both load, the unfixed copy in
`styles.css` can override the fix and re-enable horizontal scroll.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

web/src/styles.css

@@ -2648,6 +2648,7 @@ input.leaf-rename:focus {
 }
 
 .st-tool-arg {
+  flex: 1 1 0;
   color: var(--muted);
   overflow: hidden;
   text-overflow: ellipsis;
@@ -2893,7 +2894,11 @@ input.leaf-rename:focus {
 }
 
 .st-tool-group-title {
-  flex: 0 0 auto;
+  flex: 1 1 0;
+  min-width: 0;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
   font-weight: 500;
 }