Deduplicate staged sends on live relay echo

Route live channel overlay merges through the existing pending-message
reconciliation so an authoritative echo replaces its staged row before the
mutation callback completes.

Co-authored-by: Carl <c7ebe626f000404285d3686e1dc74cc07cc60a9754a150041ba132e14bd3e2ec@buzz.block.builderlab.xyz>
Signed-off-by: Wes <wesbillman@users.noreply.github.com>

desktop/src/features/messages/lib/channelWindowStore.ts

@@ -1,4 +1,5 @@
 import type { RelayEvent } from "@/shared/api/types";
+import { reconcileIncomingMessage } from "./messageMerge";
 
 export type ChannelWindowCursor = { createdAt: number; eventId: string };
 export type ChannelWindowThreadSummary = {
@@ -214,10 +215,9 @@ export function mergeLiveChannelWindowEvent(
   }
   return {
     ...current,
-    liveOverlay: current.liveOverlay
-      .filter((candidate) => candidate.id !== event.id)
-      .concat(event)
-      .sort(compareRelayOrder),
+    liveOverlay: reconcileIncomingMessage(current.liveOverlay, event).sort(
+      compareRelayOrder,
+    ),
   };
 }
 

desktop/src/features/messages/lib/projectChannelWindow.test.mjs

@@ -213,6 +213,31 @@ test("test_reconciliation_preserves_dense_second_window_order", () => {
   );
 });
 
+test("test_live_echo_replaces_matching_staged_send", () => {
+  const harness = createHarness();
+  const pending = {
+    ...event("pending", 110),
+    content: "hello",
+    pending: true,
+  };
+  const accepted = {
+    ...event("accepted", 110),
+    content: "hello",
+    id: "c".repeat(64),
+  };
+  appendLiveEvent(harness, pending);
+  appendLiveEvent(harness, accepted);
+
+  assert.deepEqual(
+    harness.client.getQueryData(harness.messagesKey).map((item) => item.id),
+    [event("initial", 100).id, accepted.id],
+  );
+  assert.equal(
+    harness.client.getQueryData(harness.messagesKey)[1]?.localKey,
+    pending.id,
+  );
+});
+
 test("test_reconciliation_retains_identical_pending_sends", () => {
   const harness = createHarness();
   const first = {