Refactor store actions to use direct Zustand state updaters

- Remove Action union/reducer dispatch path in `store.ts`
- Extract per-action state transition helpers and apply via `setAppState`
- Update `store.test.ts` to validate behavior through `useStore` actions
506a5260dcJulius Marminge committed on 3/2/2026, 9:13:19 PM· committed by Julius Marmingeparentd4c90d6
2 files changedLine totals unavailable