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/auth/auth-machine.ts

@@ -9,62 +9,18 @@
  */
 import { setup, fromPromise, assign } from "xstate";
 
-import type { AuthMode } from "@/models/auth/auth-mode";
-import type { AuthPanelMode } from "@/models/auth/auth-panel-mode";
 import type { LoginType } from "@/models/auth/login-type";
 import { authRepository } from "@/data/repositories/auth_repository";
 import { AuthStorage } from "@/data/storage/auth/auth_storage";
 import { Result } from "@/utils/result";
 
-// ============================================================
-// Context
-// ============================================================
-export interface AuthContext {
-  /** 当前面板模式（Facebook / Email） */
-  authPanelMode: AuthPanelMode;
-  /** 内部登录模式（login / register） */
-  authMode: AuthMode;
-  email: string;
-  password: string;
-  username: string;
-  confirmPassword: string;
-  errorMessage: string | null;
-  loginType: LoginType;
-}
+import { AuthContext, initialContext } from "./auth-context";
+import type { AuthEvent } from "./auth-events";
 
-const initialContext: AuthContext = {
-  authPanelMode: "facebook",
-  authMode: "login",
-  email: "",
-  password: "",
-  username: "",
-  confirmPassword: "",
-  errorMessage: null,
-  loginType: "none",
-};
-
-// ============================================================
-// Events（事件类型名与原 Dart AuthEvent 对齐）
-// ============================================================
-export type AuthEvent =
-  // 内部 UI 事件
-  | { type: "AuthPanelModeChanged"; mode: AuthPanelMode }
-  | { type: "AuthModeChanged"; mode: AuthMode }
-  | { type: "AuthFormCleared" }
-  | { type: "AuthReset" }
-  // 业务事件（提交）
-  | { type: "AuthEmailLoginSubmitted"; email: string; password: string }
-  | {
-      type: "AuthEmailRegisterSubmitted";
-      email: string;
-      password: string;
-      username: string;
-      confirmPassword: string;
-    }
-  // 社交登录（已迁移到 NextAuth）— 业务层走 GoogleLogin / FacebookLogin 类
-  | { type: "AuthGoogleLoginSubmitted" }
-  | { type: "AuthFacebookLoginSubmitted" }
-  | { type: "AuthAppleLoginSubmitted" };
+// 重新导出 Context / Event 类型，保持 machine 文件的公共 API 不变
+export type { AuthContext } from "./auth-context";
+export { initialContext } from "./auth-context";
+export type { AuthEvent } from "./auth-events";
 
 // ============================================================
 // Helpers