feat(characters): support character-scoped conversations

src/app/chat/hooks/use-splash-latest-message-sync.ts

@@ -9,12 +9,14 @@ import { getLatestSplashMessagePreview } from "@/lib/chat/splash_latest_message_
 import { useSplashLatestMessageCache } from "@/providers/splash-latest-message-provider";
 
 export interface UseSplashLatestMessageSyncInput {
+  characterId: string;
   historyLoaded: boolean;
   loginStatus: LoginStatus;
   messages: readonly UiMessage[];
 }
 
 export function useSplashLatestMessageSync({
+  characterId,
   historyLoaded,
   loginStatus,
   messages,
@@ -26,7 +28,7 @@ export function useSplashLatestMessageSync({
   useEffect(() => {
     hasObservedInitialSnapshotRef.current = false;
     identityPromiseRef.current = null;
-  }, [loginStatus]);
+  }, [characterId, loginStatus]);
 
   useEffect(() => {
     if (!historyLoaded) return;
@@ -39,7 +41,8 @@ export function useSplashLatestMessageSync({
     const preview = getLatestSplashMessagePreview(messages);
     let cancelled = false;
 
-    identityPromiseRef.current ??= resolveSplashLatestMessageCacheIdentity();
+    identityPromiseRef.current ??=
+      resolveSplashLatestMessageCacheIdentity(characterId);
     void identityPromiseRef.current.then((identity) => {
       if (!cancelled && identity) {
         cache.set(identity, preview);
@@ -49,5 +52,5 @@ export function useSplashLatestMessageSync({
     return () => {
       cancelled = true;
     };
-  }, [cache, historyLoaded, messages]);
+  }, [cache, characterId, historyLoaded, messages]);
 }