feat(state): localStorage player prefs for story and action display

src/state/__tests__/prefs.test.ts

@@ -0,0 +1,25 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+import { getPrefs, setPrefs } from '../prefs';
+
+describe('prefs', () => {
+  beforeEach(() => {
+    vi.stubGlobal('localStorage', {
+      store: {} as Record<string, string>,
+      getItem(key: string) {
+        return this.store[key] ?? null;
+      },
+      setItem(key: string, value: string) {
+        this.store[key] = value;
+      },
+    });
+  });
+
+  it('returns defaults when localStorage empty', () => {
+    expect(getPrefs()).toEqual({ storyOpenMode: 'auto', actionDetailMode: 'inline' });
+  });
+
+  it('round-trips updated prefs', () => {
+    setPrefs({ storyOpenMode: 'manual', actionDetailMode: 'hover' });
+    expect(getPrefs().storyOpenMode).toBe('manual');
+  });
+});

src/state/prefs.ts

@@ -0,0 +1,33 @@
+const PREFS_KEY = 'idlegame:prefs:v1';
+
+export type StoryOpenMode = 'auto' | 'choices-only' | 'manual';
+export type ActionDetailMode = 'inline' | 'hover' | 'info-button';
+
+export interface GamePrefs {
+  storyOpenMode: StoryOpenMode;
+  actionDetailMode: ActionDetailMode;
+}
+
+const DEFAULTS: GamePrefs = {
+  storyOpenMode: 'auto',
+  actionDetailMode: 'inline',
+};
+
+export function getPrefs(): GamePrefs {
+  if (typeof localStorage === 'undefined') return { ...DEFAULTS };
+  try {
+    const raw = localStorage.getItem(PREFS_KEY);
+    if (!raw) return { ...DEFAULTS };
+    return { ...DEFAULTS, ...JSON.parse(raw) };
+  } catch {
+    return { ...DEFAULTS };
+  }
+}
+
+export function setPrefs(partial: Partial<GamePrefs>): GamePrefs {
+  const next = { ...getPrefs(), ...partial };
+  if (typeof localStorage !== 'undefined') {
+    localStorage.setItem(PREFS_KEY, JSON.stringify(next));
+  }
+  return next;
+}