fix(web): preserve expanded structured cards

web/src/structuredRender.ts

@@ -187,7 +187,11 @@ function statusMeta(status: string | undefined, hasDiff: boolean): { text: strin
   return null;
 }
 
-function buildToolRow(row: TranscriptRow, expanded: boolean): HTMLElement {
+function buildToolRow(
+  row: TranscriptRow,
+  expanded: boolean,
+  onExpandedChange?: (expanded: boolean) => void,
+): HTMLElement {
   const tool = (row.data ?? {}) as AcpToolCallLike;
   const content = tool.content ?? [];
   const hasDiff = content.some((c) => c.type === "diff");
@@ -259,6 +263,7 @@ function buildToolRow(row: TranscriptRow, expanded: boolean): HTMLElement {
   };
   head.addEventListener("click", () => {
     setExpanded(head.getAttribute("aria-expanded") !== "true");
+    onExpandedChange?.(head.getAttribute("aria-expanded") === "true");
   });
   setExpanded(expanded);
 
@@ -363,11 +368,12 @@ function buildApprovalRow(row: TranscriptRow, approval: ApprovalRowState): HTMLE
 }
 
 /** Build the DOM for one transcript row. `approval` is consulted only for an
- *  `approval` row; pass it whenever the row might be that kind. */
+ *  `approval` row; tool expansion is supplied and reported explicitly. */
 export function buildTranscriptRow(
   row: TranscriptRow,
   approval?: ApprovalRowState,
   toolExpanded = false,
+  onToolExpandedChange?: (expanded: boolean) => void,
 ): HTMLElement {
   let built: HTMLElement;
   switch (row.kind) {
@@ -382,7 +388,7 @@ export function buildTranscriptRow(
       break;
     case "tool_call":
     case "tool_diff":
-      built = buildToolRow(row, toolExpanded);
+      built = buildToolRow(row, toolExpanded, onToolExpandedChange);
       break;
     case "approval":
       built = buildApprovalRow(row, approval ?? { pending: false, onDecide: () => Promise.resolve() });