fix: a WRAP_ETH says where its ETH goes (closes #747)

A WRAP_ETH into the router now always reads `Moved to: The router`. That is
true whichever step then takes the WETH. Other takes keep
`The swap step that spends it`.

A later WRAP_ETH of CONTRACT_BALANCE to anyone but the router now gets a
`Moved from the sender` line reading `All the ETH the transaction carries`,
and `Moved to` names the recipient. It gets none after an UNWRAP_WETH into
the router, or while the router holds ETH from a V4 step.

README states both rules.

Model: opus-5-5

README.md

@@ -1414,15 +1414,19 @@ when both tokens are known. The lines are:
   the sender that the `Amount` line does not include. The same three lines show
   what a `PERMIT2_TRANSFER_FROM` moves and where. A `WRAP_ETH` can pay its WETH
   to a recipient other than the router. When its amount gets these lines, its
-  `Moved to` line names that recipient, or reads `The sender`. A `WRAP_ETH`
-  after the step that sets `Token In` takes the amount it states from the
-  sender. When it pays anyone but the router, that amount gets these lines. When
-  it pays the router, that amount joins the `Amount` line if `Token In` is ETH,
-  and gets these lines if not. A later `WRAP_ETH` of `CONTRACT_BALANCE` states
-  no amount, so it gets no lines. ETH that the sender pays a V4 step or a
-  `WRAP_ETH` of a stated amount can get these three lines when the router may
-  hold ETH from an earlier step. When the decoder knows the amount, its
-  `Moved from the sender` line reads `Up to` and the amount.
+  `Moved to` line names that recipient, or reads `The sender`. For a `WRAP_ETH`
+  into the router, `Moved to` reads `The router`. A `WRAP_ETH` after the step
+  that sets `Token In` takes the amount it states from the sender. When it pays
+  anyone but the router, that amount gets these lines. When it pays the router,
+  that amount joins the `Amount` line if `Token In` is ETH, and gets these lines
+  if not. A later `WRAP_ETH` of `CONTRACT_BALANCE` to anyone but the router gets
+  these lines. It gets none after an `UNWRAP_WETH` into the router, or while the
+  router holds ETH from a V4 step. When it gets them, its
+  `Moved from the sender` line reads `All the ETH the transaction carries`. ETH
+  that the sender pays a V4 step or a `WRAP_ETH` of a stated amount can get
+  these three lines when the router may hold ETH from an earlier step. When the
+  decoder knows the amount, its `Moved from the sender` line reads `Up to` and
+  the amount.
 - `Permit2 allowance`, `Allowance token` and `Allowance spender`: each allowance
   that a `PERMIT2_PERMIT` or `PERMIT2_PERMIT_BATCH` grants, unless the permit's
   amount already stands as the `Amount` figure.