feat(inspect-ui): hierarchy + html panels in run detail

HierarchyPanel renders the captured DOM/AX tree with a filter input.
HtmlPanel renders the per-step HTML in an iframe (sandboxed) with a
toggle to view source. HTML tab only shows when the step actually has
HTML captured.

inspect-ui/src/panels/HtmlPanel.css

@@ -0,0 +1,60 @@
+.html-panel {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+}
+
+.html-toolbar {
+  display: flex;
+  gap: 4px;
+}
+
+.html-tab {
+  font-family: var(--font-mono);
+  font-size: 12px;
+  padding: 2px 10px;
+  background: var(--surface-1);
+  border: 1px solid var(--border);
+  color: var(--text-secondary);
+  cursor: pointer;
+}
+
+.html-tab-active {
+  color: var(--text-primary);
+  border-color: var(--border-strong, var(--border));
+}
+
+.html-frame {
+  width: 100%;
+  height: 480px;
+  border: 1px solid var(--border);
+  background: white;
+}
+
+.html-source {
+  font-family: var(--font-mono);
+  font-size: 11px;
+  color: var(--text-primary);
+  background: var(--surface-1);
+  border: 1px solid var(--border);
+  padding: 8px;
+  margin: 0;
+  max-height: 480px;
+  overflow: auto;
+  white-space: pre-wrap;
+  word-break: break-all;
+}
+
+.html-empty {
+  font-family: var(--font-mono);
+  font-size: 12px;
+  color: var(--text-secondary);
+  padding: 16px;
+}
+
+.html-error {
+  font-family: var(--font-mono);
+  font-size: 12px;
+  color: var(--text-violation, #c33);
+  padding: 16px;
+}