[Bug] prefsStore.onRehydrateStorage callback is dead code — new notification types added to the codebase are never enabled by default for existing users #129

Why this matters now

The notification system is listed as shipped in the current roadmap. mergeNotificationDefaults exists precisely to ensure that when a new notification type (e.g., PROOF_TIMEOUT) is added, existing users who upgrade get that type enabled rather than silently missing notifications. But the onRehydrateStorage callback that calls mergeNotificationDefaults is wired incorrectly for Zustand v4's API and never executes.

Problem / What

src/store/prefsStore.ts:

onRehydrateStorage: () => (persisted, error) => {
  if (error != null || !persisted) { return; }
  const merged = mergeNotificationDefaults(persisted.notificationPrefs);
  usePrefsStore.setState({ notificationPrefs: merged });
},

Zustand v4's persist middleware calls onRehydrateStorage with (state) => void, not with () => (state, error) => void. The outer () => returns a function, but Zustand v4 calls the return value with only state, not (state, error). The inner function is therefore invoked as (persisted) where persisted is the state and error is always undefined — but the outer arrow function is the one actually registered, and its body (return (persisted, error) => {...}) is simply returning a function that Zustand ignores. The setState call never runs.

The fix is to use the Zustand v4 signature directly:

onRehydrateStorage: (state) => {
  if (!state) { return; }
  usePrefsStore.setState({ notificationPrefs: mergeNotificationDefaults(state.notificationPrefs) });
},

Key Challenges

• The fix is a Zustand API subtlety; the test in prefsStore.test.ts must verify the actual post-rehydration store state, not just that the function was called.
• Confirm the onRehydrateStorage signature against the installed Zustand version (package.json) to use the correct form.
• After the fix, run the existing prefsStore.test.ts — it likely passes vacuously because the dead code never ran before.

Acceptance Criteria

• After rehydration with a stored notificationPrefs that is missing the PROOF_TIMEOUT key, the store contains PROOF_TIMEOUT: true.
• After rehydration with a stored notificationPrefs that has REWARD_CONFIRMED: false, that preference is preserved (not overwritten by defaults).
• prefsStore.test.ts has explicit assertions for both cases above.
• No other onRehydrateStorage side effects are introduced.

Relevant files / functions

• src/store/prefsStore.ts — onRehydrateStorage, mergeNotificationDefaults
• src/__tests__/prefsStore.test.ts — extend with rehydration tests

Out of scope

• Adding new notification types.
• Changes to quietHours or scheduledNotificationIds persistence.