Summary

Fixes
https://www.notion.so/cownation/Safe-WC-iOS-app-reject-approval-long-error-34c8da5f04ca8041998de02db4e10dde?v=2fc8da5f04ca81ada4ca000c320d51ef&source=copy_link

When rejecting an approval transaction in Safe iOS wallet via WalletConnect, the user sees a long, verbose error message containing raw request arguments
(addresses, data, gas, function signatures) instead of a clean rejection message.

This PR improves rejection detection and error display for viem-wrapped errors.

To Test

1. Connect to CoW Swap using Safe iOS app via WalletConnect

• Initiate an approve TX
• Reject signing the TX in the wallet
• Verify the error shown is "User rejected approval transaction" instead of a long RPC error with request arguments

2. Verify other wallet rejection flows still work

• Reject an approval with MetaMask — should show "User rejected approval transaction"
• Reject a swap/signing with any wallet — should show clean rejection message

Background

Viem wraps provider errors in ContractFunctionExecutionError which includes all request arguments in error.message. The previous rejection detection had two
issues:

1. Cause chain traversal was gated on instanceof Error — viem/WalletConnect can nest plain objects in the cause chain, which were not traversed
2. Viem's details property was not checked — viem stores the original provider error message in error.details, which may contain the rejection signal

As a safety net, the error display now uses viem's error.shortMessage (which omits request arguments) instead of error.message for non-rejection errors.