fix: a V4 SETTLE of ETH paid from the router reads as moved from the sender (closes #682)

V4Router pays a SETTLE of ETH from the router's own ETH, whichever payer
it names. The router holds the transaction's value. So a SETTLE of ETH
that names the router as payer now counts as paid by the user.

When an earlier step left ETH in the router, such a SETTLE gets lines of
its own. Its line reads "Up to" and its amount, and that amount never
joins the Amount total. A SETTLE of CONTRACT_BALANCE reads as an amount
the decoder does not know.

One existing row in tests/uniswapRecipient.test.js now expects the ETH
lines. Its SETTLE spends all the router's ETH, the transaction's value
included.

Model: opus-5-5

README.md

@@ -3473,8 +3473,11 @@ Currently supported:
   the user's wallet. Every V4 step, with a swap action or without, takes from
   the user's wallet what its `SETTLE`s paid by the user (`payerIsUser` true) and
   its `SETTLE_ALL`s pay, for each token on its own; what the step that sets the
-  input side takes of any other token counts as a later step's take. A `SETTLE`
-  of any amount but `OPEN_DELTA` pays that amount, and a `SETTLE` of
+  input side takes of any other token counts as a later step's take. A V4
+  `SETTLE` of ETH paid from the router still takes from the user's wallet, since
+  the router holds the transaction's value. When an earlier step left ETH in the
+  router, such a `SETTLE` gets lines of its own, with `Up to` before its amount.
+  A `SETTLE` of any amount but `OPEN_DELTA` pays that amount, and a `SETTLE` of
   `OPEN_DELTA` or a `SETTLE_ALL` pays what the step owes, as above. So a V4 step
   that swaps 400 USDT, with a `SETTLE` of 5,000 USDT paid by the user and the
   rest taken to another address, reads `5000.0000 USDT`. A later step paid from