fix(app): synchronize chat submission and keyboard state

Render optimistic turn feedback before host acknowledgement and roll it back on rejection. Reconcile iOS keyboard offsets from the native transition end event so JS contention cannot leave the composer displaced.

packages/app/src/composer/actions.ts

@@ -186,40 +186,50 @@ export async function dispatchComposerAgentMessage(
     images: wirePayload.images,
     attachments: wirePayload.attachments,
   });
-  appendUserMessageToStream(input.agentId, userMessage, input.stream);
-  const imagesData = await input.encodeImages(wirePayload.images);
-  await input.client.sendAgentMessage(input.agentId, input.text, {
-    messageId,
-    images: imagesData ?? [],
-    attachments: wirePayload.attachments,
-  });
+  const rollbackOptimisticMessage = appendUserMessageToStream(
+    input.agentId,
+    userMessage,
+    input.stream,
+  );
+  try {
+    const imagesData = await input.encodeImages(wirePayload.images);
+    await input.client.sendAgentMessage(input.agentId, input.text, {
+      messageId,
+      images: imagesData ?? [],
+      attachments: wirePayload.attachments,
+    });
+  } catch (error) {
+    rollbackOptimisticMessage();
+    throw error;
+  }
 }
 
 function appendUserMessageToStream(
   agentId: string,
   userMessage: UserMessageItem,
   stream: AgentStreamWriter,
-): void {
+): () => void {
   const result = appendOptimisticUserMessageToStream({
     tail: stream.getTail(agentId) ?? [],
     head: stream.getHead(agentId) ?? [],
     message: userMessage,
     placement: "active-head",
   });
-  if (result.changedHead) {
-    stream.setHead((prev) => {
-      const next = new Map(prev);
-      next.set(agentId, result.head);
-      return next;
+  const write = result.changedHead ? stream.setHead : stream.setTail;
+  const items = result.changedHead ? result.head : result.tail;
+  write((prev) => new Map(prev).set(agentId, items));
+
+  return () => {
+    write((prev) => {
+      const current = prev.get(agentId);
+      if (!current) return prev;
+      const nextItems = current.filter(
+        (item) => item.id !== userMessage.id || item.kind !== "user_message" || !item.optimistic,
+      );
+      if (nextItems.length === current.length) return prev;
+      return new Map(prev).set(agentId, nextItems);
     });
-  }
-  if (result.changedTail) {
-    stream.setTail((prev) => {
-      const next = new Map(prev);
-      next.set(agentId, result.tail);
-      return next;
-    });
-  }
+  };
 }
 
 export interface QueueComposerMessageInput {