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
