refactor(stores): split state and event unions into separate files

Extract `<Name>Context` interface + `initialContext` const into
`<name>-context.ts` and the event union into `<name>-events.ts` for
all four state machines (auth, chat, sidebar, user) under src/stores/.

- `*-machine.ts` keeps helpers, actors, actions, and the
  `setup().createMachine()` body; re-exports the types/initial value
  to preserve its public API.
- `*-types.ts` re-exports from the new files for backward compatibility
  (sidebar keeps enum re-exports, chat keeps GuestChatQuota).
- `index.ts` barrels updated to re-export the new files.
- Removed unused model imports (AuthMode, AuthPanelMode) from
  auth-machine.ts; kept LoginType, UiMessage, UserView where still
  used by actors/helpers.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/stores/user/index.ts

@@ -5,7 +5,10 @@
  *   - 业务类（Dart 风格 context/reducer/side-effects）已合并到 user-machine.ts
  *   - 类型由 user-types.ts 重新导出
  *   - React 入口为 user-context.tsx（useMachine 包装）
+ *   - Context 形状与初始值位于 user-context.ts
+ *   - 事件联合位于 user-events.ts
  */
 export * from "./user-context";
+export * from "./user-events";
 export * from "./user-types";
 export { userMachine } from "./user-machine";

src/stores/user/user-context.ts

@@ -0,0 +1,20 @@
+/**
+ * User 状态机：Context 形状 + 初始值
+ */
+import type { UserView } from "@/models/user/user";
+
+export interface UserContext {
+  currentUser: UserView | null;
+  pronouns: string;
+  coinBalance: number;
+  isLoading: boolean;
+  avatarUrl: string | null;
+}
+
+export const initialContext: UserContext = {
+  currentUser: null,
+  pronouns: "He",
+  coinBalance: 45,
+  isLoading: false,
+  avatarUrl: null,
+};

src/stores/user/user-events.ts

@@ -0,0 +1,14 @@
+/**
+ * User 状态机：事件联合
+ */
+import type { UserView } from "@/models/user/user";
+
+export type UserEvent =
+  | { type: "UserInit" }
+  | { type: "UserFetch" }
+  | { type: "UserUpdate"; user: UserView }
+  | { type: "UserUpdateUsername"; username: string }
+  | { type: "UserUpdatePronouns"; pronouns: string }
+  | { type: "UserLogout" }
+  | { type: "UserDeleteChatHistory" }
+  | { type: "UserDeleteAccount" };

src/stores/user/user-machine.ts

@@ -17,37 +17,13 @@ import { authRepository } from "@/data/repositories/auth_repository";
 import { UserStorage } from "@/data/storage/user/user_storage";
 import { Result } from "@/utils/result";
 
-// ============================================================
-// Context
-// ============================================================
-export interface UserContext {
-  currentUser: UserView | null;
-  pronouns: string;
-  coinBalance: number;
-  isLoading: boolean;
-  avatarUrl: string | null;
-}
+import { UserContext, initialContext } from "./user-context";
+import type { UserEvent } from "./user-events";
 
-const initialContext: UserContext = {
-  currentUser: null,
-  pronouns: "He",
-  coinBalance: 45,
-  isLoading: false,
-  avatarUrl: null,
-};
-
-// ============================================================
-// Events
-// ============================================================
-export type UserEvent =
-  | { type: "UserInit" }
-  | { type: "UserFetch" }
-  | { type: "UserUpdate"; user: UserView }
-  | { type: "UserUpdateUsername"; username: string }
-  | { type: "UserUpdatePronouns"; pronouns: string }
-  | { type: "UserLogout" }
-  | { type: "UserDeleteChatHistory" }
-  | { type: "UserDeleteAccount" };
+// 重新导出 Context / Event 类型，保持 machine 文件的公共 API 不变
+export type { UserContext } from "./user-context";
+export { initialContext } from "./user-context";
+export type { UserEvent } from "./user-events";
 
 // ============================================================
 // Helpers

src/stores/user/user-types.ts

@@ -3,7 +3,8 @@
  *
  * 原始文件定义了 UserState 接口、UserEvent 联合、initialUserState。
  * 状态机重构后：
- *   - `UserEvent` 联合由 `user-machine.ts` 重新导出（保留类型）
+ *   - `UserEvent` 联合由 `user-events.ts` 导出
+ *   - Context 形状与初始值由 `user-context.ts` 导出
  *   - `UserState` 由 `user-context.tsx` 导出（保持原 API 兼容）
  */
-export type { UserEvent } from "./user-machine";
+export type { UserEvent } from "./user-events";