Render Mermaid diagrams and worktree images in agent Markdown

web/style.css

@@ -644,6 +644,19 @@ button.compact.danger {
   overflow-x: auto;
 }
 
+.md-img img {
+  display: block;
+  max-width: 100%;
+  max-height: 480px;
+  margin: 4px 0;
+  border: 1px solid var(--border);
+  border-radius: 6px;
+}
+
+.md-img-missing {
+  color: var(--muted);
+}
+
 .md table {
   border-collapse: collapse;
 }
@@ -1194,6 +1207,22 @@ pre.diff .meta {
   background: var(--surface);
   padding: 6px 8px;
   border-radius: 6px;
+  overflow-x: auto;
+}
+
+.mermaid-diagram {
+  margin: 0 0 8px;
+  overflow-x: auto;
+}
+
+.mermaid-diagram svg {
+  display: block;
+  max-width: 100%;
+  height: auto;
+}
+
+.mermaid-error {
+  color: var(--muted);
 }
 
 .caption {