Adds a test that constructs a Uniswap V4 USDT→USDC swap using
SETTLE/SWAP_EXACT_IN_SINGLE/TAKE sub-actions inside a V4_SWAP command.
Without decodeV4Swap(), the output token would be unresolvable and the
swap name would not show 'USDT → USDC'. This test fails on the old code
and passes with the decodeV4Swap() fix.
Refs: #59
Replace stub error handlers with full approval flow for personal_sign,
eth_sign, eth_signTypedData_v4, and eth_signTypedData. Uses toolbar
popup only (no fallback window) and keeps sign approvals pending across
popup close/reopen cycles so the user can respond via the toolbar icon.
