fix: persist completed item visibility

frontend/src/lib/mvp-utils.test.ts

@@ -1,5 +1,5 @@
 import { describe, expect, it } from 'vitest'
-import { calendarModeLabel, clampFabPosition, countdownDayText, countdownKindLabel, dateKey, defaultView, habitButtonNotice, habitButtonValue, habitWeek, isFabDrag, isHabitComplete, isHabitScheduledToday, isTaskView, nextHabitSwipeValue, nextTotalAfterLocalTaskAdd, numericHabitInputValue, previousHabitSwipeValue, quickTaskFields, readCountdownCache, readHabitGridCache, shouldToggleRowSwipe, writeCountdownCache, writeHabitGridCache } from './mvp-utils'
+import { calendarModeLabel, clampFabPosition, countdownDayText, countdownKindLabel, dateKey, defaultView, habitButtonNotice, habitButtonValue, habitWeek, isFabDrag, isHabitComplete, isHabitScheduledToday, isTaskView, nextHabitSwipeValue, nextTotalAfterLocalTaskAdd, numericHabitInputValue, previousHabitSwipeValue, quickTaskFields, readCountdownCache, readHabitGridCache, readStoredBoolean, shouldToggleRowSwipe, writeCountdownCache, writeHabitGridCache, writeStoredBoolean } from './mvp-utils'
 
 describe('MVP view utilities', () => {
   it('formats a local date as YYYY-MM-DD', () => {
@@ -77,6 +77,19 @@ describe('MVP view utilities', () => {
     expect(habitButtonNotice('boolean', 1, 0)).toBe('已取消完成')
   })
 
+  it('persists boolean display preferences across page refreshes', () => {
+    const storage = new Map<string, string>()
+    const fakeStorage = {
+      getItem: (key: string) => storage.get(key) ?? null,
+      setItem: (key: string, value: string) => storage.set(key, value),
+    }
+    expect(readStoredBoolean(fakeStorage, 'dodo.show-completed', true)).toBe(true)
+    writeStoredBoolean(fakeStorage, 'dodo.show-completed', false)
+    expect(readStoredBoolean(fakeStorage, 'dodo.show-completed', true)).toBe(false)
+    storage.set('dodo.show-completed', 'invalid')
+    expect(readStoredBoolean(fakeStorage, 'dodo.show-completed', true)).toBe(true)
+  })
+
   it('reuses the current week habit grid while refreshing in the background', () => {
     const habits = [{ id: 'habit-1', name: '喝水' }]
     writeHabitGridCache('2026-09-07', habits)