Documentation Request: Add guidance on error surfaces and user-facing messaging for common OnchainKit failures

### Is your documentation request related to a problem? Please describe.

OnchainKit exposes multiple user-facing failure modes (wallet not connected, wrong network, rejected signature, insufficient funds, RPC errors). However, there is no centralized guidance on how these errors are surfaced or how apps should translate them into clear, user-friendly messages

Developers often ask:
- which errors are expected vs exceptional
- which errors should be shown directly to users
- how to map low-level errors to friendly UI copy
- how to keep messaging consistent across components and hooks

### Proposed Solution

- Add a documentation section (e.g., “Error Handling & UX Guidelines”).
- Categorize common errors (connection, network, user rejection, balance, RPC).
- Provide recommended user-facing message examples for each category.
- Include guidance on when to retry vs prompt user action.
- Reference existing components/hooks where applicable.