fix: a swap's unknown first take shows beside a PERMIT2_TRANSFER_FROM, only when the user pays it (closes #634)

decode() now records whether the user pays the V4 step that sets the
input side any of its input token, and decides once, after the loop,
whether that step counts as a take from the sender. A stated amount
counts whoever pays it; with none stated, the step counts only when the
user pays it. Paid from the router, it gets no Moved from the sender
lines, with a PERMIT2_PERMIT of another token or without. When it counts
and states no amount, its Unknown (could not be decoded) line also shows
beside a PERMIT2_TRANSFER_FROM of its token, whose figure is on that
move's own lines or, into the router, on its Paid to line. README
Transaction Decoding says the same.

Model: opus-5-5

tests/uniswap.test.js

@@ -2415,7 +2415,7 @@ describe("uniswap decoder", () => {
                     V4_EXACT_OUT_600_FROM_ROUTER,
                     V2_EXACT_OUT_400,
                 ],
-                lines: [["Amount", "Up to 1.0000 DAI"], ...UP_TO_400_USDT],
+                lines: [["Amount", "1.0000 DAI"], ...UP_TO_400_USDT],
             },
         ])(
             "$kind, gives the V4 step no lines of its own",