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/chat/chat-machine.ts

@@ -23,32 +23,8 @@ import { AuthStorage } from "@/data/storage/auth/auth_storage";
 import { formatDate } from "@/utils/date";
 import { Result } from "@/utils/result";
 
-// ============================================================
-// Context
-// ============================================================
-export interface ChatContext {
-  messages: UiMessage[];
-  isReplyingAI: boolean;
-  isGuest: boolean;
-  guestRemainingQuota: number;
-  guestTotalQuota: number;
-  quotaExceededTrigger: number;
-  isLoadingMore: boolean;
-  hasMore: boolean;
-  historyOffset: number;
-}
-
-const initialContext: ChatContext = {
-  messages: [],
-  isReplyingAI: false,
-  isGuest: true,
-  guestRemainingQuota: 40,
-  guestTotalQuota: 50,
-  quotaExceededTrigger: 0,
-  isLoadingMore: false,
-  hasMore: true,
-  historyOffset: 0,
-};
+import { ChatContext, initialContext } from "./chat-context";
+import type { ChatEvent } from "./chat-events";
 
 /** 游客配额阈值（与 Dart `GuestChatQuota` 保持一致） */
 export const GuestChatQuota = {
@@ -56,27 +32,10 @@ export const GuestChatQuota = {
   quotaExhausted: 0,
 } as const;
 
-// ============================================================
-// Events
-// ============================================================
-export type ChatEvent =
-  | { type: "ChatInit" }
-  | { type: "ChatScreenVisible" }
-  | { type: "ChatScreenInvisible" }
-  | { type: "ChatSendMessage"; content: string }
-  | { type: "ChatSendImage"; imageBase64: string }
-  | { type: "ChatLoadMoreHistory" }
-  | {
-      type: "ChatAISentenceReceived";
-      index: number;
-      text: string;
-      total: number;
-      done: boolean;
-    }
-  | { type: "ChatWebSocketError"; errorMessage: string }
-  | { type: "ChatWebSocketConnected"; userId: string }
-  | { type: "ChatQuotaExceeded" }
-  | { type: "ChatAuthStatusChanged" };
+// 重新导出 Context / Event 类型，保持 machine 文件的公共 API 不变
+export type { ChatContext } from "./chat-context";
+export { initialContext } from "./chat-context";
+export type { ChatEvent } from "./chat-events";
 
 // ============================================================
 // Helpers