fix(signal): fall back to dataMessage.timestamp for ACK reaction

Mirror the same timestamp fallback already used for read receipts:
  envelope.timestamp ?? dataMessage.timestamp

Messages that carry only dataMessage.timestamp (no envelope.timestamp)
previously skipped the ACK entirely; they now receive one correctly.

Updates the 'timestamp missing' test to require both timestamps absent,
and adds a new test confirming the dataMessage fallback path.

Addresses: https://github.com/openclaw/openclaw/pull/31078#discussion_r2871998637

extensions/signal/src/monitor/event-handler.ack-reaction.test.ts

@@ -173,13 +173,32 @@ describe("Signal ACK reactions", () => {
     expect(sendReactionSignal).not.toHaveBeenCalled();
   });
 
-  it("does NOT send ack when timestamp is missing", async () => {
+  it("sends ack using dataMessage.timestamp when envelope.timestamp is missing", async () => {
     const deps = makeDeps();
     const handler = createSignalEventHandler(deps);
     await handler(
       makeEvent({
         timestamp: undefined,
-        dataMessage: { message: "hello", timestamp: 1700000000000 },
+        dataMessage: { message: "hello", timestamp: 1700000001234 },
+      }),
+    );
+
+    expect(sendReactionSignal).toHaveBeenCalledTimes(1);
+    expect(sendReactionSignal).toHaveBeenCalledWith(
+      expect.any(String),
+      1700000001234,
+      expect.any(String),
+      expect.any(Object),
+    );
+  });
+
+  it("does NOT send ack when both envelope and dataMessage timestamps are missing", async () => {
+    const deps = makeDeps();
+    const handler = createSignalEventHandler(deps);
+    await handler(
+      makeEvent({
+        timestamp: undefined,
+        dataMessage: { message: "hello", timestamp: undefined },
       }),
     );
 

extensions/signal/src/monitor/event-handler.ts

@@ -708,14 +708,22 @@ export function createSignalEventHandler(deps: SignalEventHandlerDeps) {
       messageText || dataMessage.attachments?.length || dataMessage.quote?.text?.trim(),
     );
 
+    // Resolve ACK timestamp — mirror the same fallback used for read receipts.
+    const ackTimestamp =
+      typeof envelope.timestamp === "number"
+        ? envelope.timestamp
+        : typeof dataMessage.timestamp === "number"
+          ? dataMessage.timestamp
+          : undefined;
+
     // Send ACK reaction immediately — before any awaited I/O (attachment fetch, read receipt)
     // so the user gets instant visual feedback that their message was received.
-    if (hasEarlyBody && typeof envelope.timestamp === "number") {
+    if (hasEarlyBody && ackTimestamp !== undefined) {
       maybeSendSignalAckReaction({
         cfg: deps.cfg,
         agentId: route.agentId,
         senderRecipient,
-        targetTimestamp: envelope.timestamp,
+        targetTimestamp: ackTimestamp,
         isGroup,
         groupId,
         wasMentioned: effectiveWasMentioned,