fix(examples): harden empty wallet accounts on connect

[kutluhaneth46]

Summary

• Harden App Kit connect helpers so an empty account list cannot look connected
• Prefer accounts returned by eth_requestAccounts, fall back to eth_accounts, and throw when no account is available so the catch path keeps action buttons disabled
• Apply the same address-required rule for Solana connect in app-kit-bridge-solana
• Cover send, swap, EVM bridge, and Solana bridge examples with focused helper tests

Complementary to #6 / #7 (retry-after-rejection). This PR targets the empty-account / false-connected path rather than permission rejection alone.

Test plan

• cd app-kit-send && npm install && npm test
• cd app-kit-swap && npm install && npm test
• cd app-kit-bridge-evm && npm install && npm test
• cd app-kit-bridge-solana && npm install && npm test
• Manually reject/empty-account connect and confirm UI stays disconnected with retryable connect buttons

[hjchen-circle]

We acknowledge the issue raised in #6, but the scope of the proposed fix goes far beyond the original issue. Closing the PR. The issue is resolved in #9