fix: the approval screen names the address a swap's output is paid to (closes #594)

The swap decoder read no recipient, so a swap paying its output to another
address still showed Min. received. It now reads the recipient of every swap
step, SWEEP, UNWRAP_WETH, V4 TAKE and TAKE_ALL, reads the router's
placeholders as the router does (address(1) is the sender, address(2) the
router, which holds the output until a later SWEEP or UNWRAP_WETH pays it
out), and compares the result with the transaction's sender. When the output
goes anywhere else, a Paid to line names each address it is paid to and the
minimum reads Min. paid out. The approval and transaction detail screens pass
the sender in.

Model: opus-5-5

README.md

@@ -1144,8 +1144,9 @@ fetched, without that cross-address check, and shows the row's figure.
 
 **Decoded amount lines on the transaction approval screen:** the `Amount` line
 of a decoded ERC-20 call, and the `Amount` and `Min. received` lines of a
-decoded swap (see TxApproval below), do not always read as a number. They can
-read:
+decoded swap (see TxApproval below; `Min. received` reads `Min. paid out` when
+the output is paid to another address, see Transaction Decoding), do not always
+read as a number. They can read:
 
 - A formatted quantity, e.g. `17.1900 USDT`, when the token's scale is known:
   truncated to four decimals, with the floor and the zero cases described above.
@@ -2279,7 +2280,9 @@ view would leave a wallet one click from deletion.
     - Site origin (bold, scheme and port included) + "wants to send a
       transaction"
     - Decoded action (if calldata is recognized): action name, token details,
-      amounts, steps, deadline (see Transaction Decoding)
+      amounts, steps, deadline, and for a swap whose output is paid to an
+      address other than the From address, each address it is paid to (see
+      Transaction Decoding)
     - From: color dot + full address + etherscan link
     - Contract: color dot + full address + etherscan link, token symbol label if
       known; for a contract creation, the same sentence as on WaitTx
@@ -2914,7 +2917,24 @@ Currently supported:
   listed as `Execute Sub-Plan (its steps are not shown)`, and whatever the other
   steps state, the summary names no swap direction, `Token In` and `Token Out`
   read `Unknown (could not be decoded)`, and there is no `Amount` or
-  `Min. received` line.
+  `Min. received` line. Each swap step, `SWEEP`, `UNWRAP_WETH` and V4 `TAKE`
+  names the address it pays, and `TAKE_ALL` pays the transaction's sender. The
+  router reads two of those addresses as placeholders: `address(1)` is the
+  transaction's sender, and `address(2)` is the router itself, which holds what
+  it is paid until a later step pays it out. The output is paid to the address
+  of the step that sets the output side (for a V4 step, of every `TAKE` and
+  `TAKE_ALL` of its output currency), or, when no step sets it, of the
+  `UNWRAP_WETH` that makes `Token Out` ETH. While the router holds it, the next
+  `SWEEP` of the output token, or `UNWRAP_WETH` of a WETH output, pays it to
+  that step's address. A `BALANCE_CHECK_ERC20` step pays nothing and leaves the
+  address as it was. An output nothing pays out is paid to the router. When the
+  output is paid to any address other than the transaction's sender (the From
+  address on TxApproval, the sender the explorer reports on TransactionDetail),
+  a `Paid to` line after `Token Out` names each address it is paid to, the
+  sender's included, and `Min. received` reads `Min. paid out`. A swap paid to
+  the sender, directly or through the router, has neither. The decoder does not
+  read `TRANSFER`, `PAY_PORTION` or V4 `TAKE_PORTION`, each of which pays an
+  amount or a share to an address of its own.
 
 ### Non-Goals Forever