feat(react19): useOptimistic integration and useActionState patterns for thunks

[ctrlplusb]

Summary

Explore and document React 19's useOptimistic and useActionState patterns for use with easy-peasy thunks and actions.

Parent issue: #1004

Background

React 19 introduces useOptimistic for optimistic UI updates and useActionState for form-based action state management. Both have natural synergies with easy-peasy's thunk pattern.

Areas to explore

1. useOptimistic integration

• Natural fit for thunk-based patterns: optimistically apply a state change, then reconcile when the thunk resolves or roll back on failure
• Could provide a useStoreOptimistic(selector, applyOptimistic) hook
• Challenge: Deep integration would require easy-peasy to expose a way to "preview" state changes without committing, which isn't trivially compatible with the Redux dispatch model
• May be more practical as a documented pattern showing how to compose useOptimistic with useStoreState

2. useActionState patterns

• Designed for form actions with server/client transitions, returning [state, formAction, isPending]
• easy-peasy thunks could be wrapped in useActionState for form submission patterns
• This is primarily a consumer-side concern — may not require library changes
• Document recommended patterns for combining useActionState with easy-peasy actions

Deliverables

• Evaluate whether library-level hooks are warranted or if documentation/examples suffice
• If hooks are warranted, implement with factory creators and TypeScript definitions
• Add documentation/examples showing integration patterns
• Consider adding to the easy-peasy website/docs

Testing

• Test optimistic update + rollback patterns with async thunks
• Test useActionState wrapping of easy-peasy actions in form contexts
• Verify patterns work correctly with React 19 concurrent features