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)

frontend/src/lib/mvp-utils.ts

@@ -1,3 +1,18 @@
+type BooleanStorage = Pick<Storage, 'getItem' | 'setItem'>
+
+export function readStoredBoolean(storage: BooleanStorage, key: string, fallback: boolean) {
+  try {
+    const value = storage.getItem(key)
+    if (value === 'true') return true
+    if (value === 'false') return false
+  } catch { /* storage may be unavailable */ }
+  return fallback
+}
+
+export function writeStoredBoolean(storage: BooleanStorage, key: string, value: boolean) {
+  try { storage.setItem(key, String(value)) } catch { /* storage may be unavailable */ }
+}
+
 export function dateKey(date: Date) {
   const y = date.getFullYear()
   const m = `${date.getMonth() + 1}`.padStart(2, '0')