feat(desktop): add RecoveryStateStore with subscriber lifecycle

packages/desktop/src/recovery.ts

@@ -0,0 +1,64 @@
+export type RecoveryReasonCode =
+  | 'load-failed'
+  | 'render-gone'
+  | 'unresponsive'
+  | 'renderer-stalled';
+
+export type UpdateState =
+  | 'idle'
+  | 'checking'
+  | 'downloading'
+  | 'downloaded'
+  | 'error';
+
+export interface RecoveryState {
+  mode: 'normal' | 'recovery';
+  reason: { code: RecoveryReasonCode; detail: string } | null;
+  updateState: UpdateState;
+  updateVersion: string | null;
+  lastUpdateError: { message: string; code: string | null; at: number } | null;
+  lastCheckResult: 'up-to-date' | 'failed' | null;
+}
+
+const INITIAL_STATE: RecoveryState = {
+  mode: 'normal',
+  reason: null,
+  updateState: 'idle',
+  updateVersion: null,
+  lastUpdateError: null,
+  lastCheckResult: null,
+};
+
+export class RecoveryStateStore {
+  private state: RecoveryState = { ...INITIAL_STATE };
+  private listeners = new Set<(s: RecoveryState) => void>();
+  private inRecoveryMode = false;
+
+  get(): Readonly<RecoveryState> {
+    return this.state;
+  }
+
+  update(partial: Partial<RecoveryState>): void {
+    this.state = { ...this.state, ...partial };
+    for (const cb of this.listeners) cb(this.state);
+  }
+
+  subscribe(cb: (s: RecoveryState) => void): () => void {
+    this.listeners.add(cb);
+    return () => { this.listeners.delete(cb); };
+  }
+
+  isInRecoveryMode(): boolean {
+    return this.inRecoveryMode;
+  }
+
+  markRecoveryEntered(): void {
+    this.inRecoveryMode = true;
+  }
+
+  markRecoveryExited(): void {
+    this.inRecoveryMode = false;
+  }
+}
+
+export const recoveryStore = new RecoveryStateStore();