fix(ai-chat): keep composer draft across new-chat id adoption remount

Typing into the composer while the agent was streaming lost the draft once
the turn finished: on a brand-new chat, adopting the freshly created chat id
changes ChatThread's key and remounts it, wiping ChatInput's local state.

Lift the composer draft into a module-level jotai atom (aiChatDraftAtom) so it
survives the remount. Reset it only on deliberate chat switches — startNewChat,
selectChat, and the page-history "AI agent" badge deep-link — so a draft never
leaks between conversations, while adoption (which goes through a useEffect)
preserves it.

apps/client/src/features/ai-chat/atoms/ai-chat-atom.ts

@@ -12,3 +12,10 @@ export const activeAiChatIdAtom = atom(null as string | null);
 
 // Whether the floating AI chat window is open. Non-persistent (resets per session).
 export const aiChatWindowOpenAtom = atom<boolean>(false);
+
+// The AI chat composer draft (text typed but not yet sent). Held here — OUTSIDE
+// ChatThread — so it survives the thread remount that happens when a brand-new
+// chat adopts its freshly created id after the first turn finishes. If it lived
+// in ChatInput's local state, that remount would wipe text the user typed while
+// the agent was still streaming. Reset on deliberate chat switches.
+export const aiChatDraftAtom = atom<string>("");

apps/client/src/features/ai-chat/components/ai-chat-window.tsx

@@ -15,13 +15,14 @@ import {
   IconPlus,
   IconX,
 } from "@tabler/icons-react";
-import { useAtom } from "jotai";
+import { useAtom, useSetAtom } from "jotai";
 import { useParams } from "react-router-dom";
 import { useTranslation } from "react-i18next";
 import { useQueryClient } from "@tanstack/react-query";
 import {
   activeAiChatIdAtom,
   aiChatWindowOpenAtom,
+  aiChatDraftAtom,
 } from "@/features/ai-chat/atoms/ai-chat-atom.ts";
 import { usePageQuery } from "@/features/page/queries/page-query.ts";
 import { extractPageSlugId } from "@/lib";
@@ -90,6 +91,7 @@ export default function AiChatWindow() {
   const queryClient = useQueryClient();
   const [windowOpen, setWindowOpen] = useAtom(aiChatWindowOpenAtom);
   const [activeChatId, setActiveChatId] = useAtom(activeAiChatIdAtom);
+  const setDraft = useSetAtom(aiChatDraftAtom);
 
   // History section starts collapsed (matches the former panel's behavior).
   const [historyOpen, setHistoryOpen] = useState(false);
@@ -131,14 +133,16 @@ export default function AiChatWindow() {
   const startNewChat = useCallback((): void => {
     setActiveChatId(null);
     setHistoryOpen(false);
-  }, [setActiveChatId]);
+    setDraft("");
+  }, [setActiveChatId, setDraft]);
 
   const selectChat = useCallback(
     (chatId: string): void => {
       setActiveChatId(chatId);
       setHistoryOpen(false);
+      setDraft("");
     },
-    [setActiveChatId],
+    [setActiveChatId, setDraft],
   );
 
   // After a turn finishes, refresh the chat list. For a brand-new chat (no id

apps/client/src/features/ai-chat/components/chat-input.tsx

@@ -1,7 +1,9 @@
-import { useState, KeyboardEvent } from "react";
+import { KeyboardEvent } from "react";
 import { ActionIcon, Group, Textarea, Tooltip } from "@mantine/core";
 import { IconPlayerStopFilled, IconSend } from "@tabler/icons-react";
 import { useTranslation } from "react-i18next";
+import { useAtom } from "jotai";
+import { aiChatDraftAtom } from "@/features/ai-chat/atoms/ai-chat-atom.ts";
 
 interface ChatInputProps {
   onSend: (text: string) => void;
@@ -22,7 +24,7 @@ export default function ChatInput({
   disabled,
 }: ChatInputProps) {
   const { t } = useTranslation();
-  const [value, setValue] = useState("");
+  const [value, setValue] = useAtom(aiChatDraftAtom);
 
   const send = (): void => {
     const text = value.trim();

apps/client/src/features/page-history/components/history-item.tsx

@@ -11,6 +11,7 @@ import { useSetAtom } from "jotai";
 import {
   activeAiChatIdAtom,
   aiChatWindowOpenAtom,
+  aiChatDraftAtom,
 } from "@/features/ai-chat/atoms/ai-chat-atom.ts";
 import { historyAtoms } from "@/features/page-history/atoms/history-atoms.ts";
 
@@ -43,6 +44,7 @@ function AiAgentBadge({
   const { t } = useTranslation();
   const setAiChatWindowOpen = useSetAtom(aiChatWindowOpenAtom);
   const setActiveChatId = useSetAtom(activeAiChatIdAtom);
+  const setDraft = useSetAtom(aiChatDraftAtom);
   const setHistoryModalOpen = useSetAtom(historyAtoms);
 
   const tooltip = t("Edited by AI agent on behalf of {{name}}", {
@@ -54,10 +56,19 @@ function AiAgentBadge({
       event.stopPropagation();
       if (!aiChatId) return;
       setActiveChatId(aiChatId);
+      // Switching to another chat must start with a clean composer — clear any
+      // unsent draft so it does not leak from the previously open chat.
+      setDraft("");
       setAiChatWindowOpen(true);
       setHistoryModalOpen(false);
     },
-    [aiChatId, setActiveChatId, setAiChatWindowOpen, setHistoryModalOpen],
+    [
+      aiChatId,
+      setActiveChatId,
+      setDraft,
+      setAiChatWindowOpen,
+      setHistoryModalOpen,
+    ],
   );
 
   const badge = (