refactor(api): 收口 server/client 数据解析层，消除 aiGenerationClient 的 as T 断言

src/api/serverConnection.ts

@@ -82,9 +82,19 @@ function parseStoredSession(raw: string | null): WebUserSession | null {
 
   try {
     const parsed = JSON.parse(raw) as unknown;
-    return isRecord(parsed) && typeof parsed.token === "string" && isRecord(parsed.user)
-      ? (parsed as unknown as WebUserSession)
-      : null;
+    // Require token + a user object with at least an id, so a malformed/partial
+    // cached session does not get cast wholesale into WebUserSession and then
+    // crash UI code that reads user.id / user.username.
+    if (!isRecord(parsed) || typeof parsed.token !== "string" || !isRecord(parsed.user)) {
+      return null;
+    }
+    const user = parsed.user;
+    const userId = user.id ?? user.userId ?? user.user_id;
+    const username = user.username ?? user.name;
+    if (userId === undefined || typeof username !== "string" || !username.trim()) {
+      return null;
+    }
+    return parsed as unknown as WebUserSession;
   } catch {
     return null;
   }