Keep attachments visible after creating an agent (#2030)

* fix(chat): keep attachments visible after creating agents

Agent creation could receive the canonical user message before the client knew the new agent ID. Hand the local rich presentation to that message and preserve it through later timeline hydration.

* refactor(chat): clarify local message presentation naming

* fix(chat): clear pending state after message handoff

packages/app/src/stores/session-store.ts

@@ -4,8 +4,7 @@ import { subscribeWithSelector } from "zustand/middleware";
 import type { DaemonClient } from "@getpaseo/client/internal/daemon-client";
 import type { AgentDirectoryEntry } from "@/types/agent-directory";
 import {
-  appendOptimisticUserMessageToStream,
-  type OptimisticUserMessagePlacement,
+  handoffCreatedAgentUserMessageToStream,
   type StreamItem,
   type UserMessageItem,
 } from "@/types/stream";
@@ -434,14 +433,10 @@ interface SessionStoreActions {
     agentId: string,
     state: { tail?: StreamItem[]; head?: StreamItem[] },
   ) => void;
-  appendOptimisticUserMessageToAgentStream: (
+  handoffCreatedAgentUserMessage: (
     serverId: string,
     agentId: string,
     message: UserMessageItem,
-    options: {
-      placement: OptimisticUserMessagePlacement;
-      skipIfUserMessageExists?: boolean;
-    },
   ) => boolean;
   clearAgentStreamHead: (serverId: string, agentId: string) => void;
   setAgentTimelineCursor: (
@@ -960,8 +955,8 @@ export const useSessionStore = create<SessionStore>()(
         });
       },
 
-      appendOptimisticUserMessageToAgentStream: (serverId, agentId, message, options) => {
-        let didAppend = false;
+      handoffCreatedAgentUserMessage: (serverId, agentId, message) => {
+        let didHandoff = false;
         set((prev) => {
           const session = prev.sessions[serverId];
           if (!session) {
@@ -970,12 +965,10 @@ export const useSessionStore = create<SessionStore>()(
 
           const currentTail = session.agentStreamTail.get(agentId) ?? [];
           const currentHead = session.agentStreamHead.get(agentId) ?? [];
-          const result = appendOptimisticUserMessageToStream({
+          const result = handoffCreatedAgentUserMessageToStream({
             tail: currentTail,
             head: currentHead,
             message,
-            placement: options.placement,
-            skipIfUserMessageExists: options.skipIfUserMessageExists,
           });
           if (!result.changedTail && !result.changedHead) {
             return prev;
@@ -987,7 +980,7 @@ export const useSessionStore = create<SessionStore>()(
           const nextHead = result.changedHead
             ? new Map(session.agentStreamHead).set(agentId, result.head)
             : session.agentStreamHead;
-          didAppend = true;
+          didHandoff = true;
 
           return {
             ...prev,
@@ -1001,7 +994,7 @@ export const useSessionStore = create<SessionStore>()(
             },
           };
         });
-        return didAppend;
+        return didHandoff;
       },
 
       clearAgentStreamHead: (serverId, agentId) => {