fix: a confirmation screen drawn again keeps the network it was reviewed for (closes #586)

ConfirmTx set the transaction's chain id to the active network's every
time it drew the screen, so a popup reopened onto a saved confirmation
after a network switch in Settings described the reviewed transfer as
the new network's and sent it there.

show() now sets the chain id only on a transaction Send hands over, and
the screen describes the transaction entirely on that network: native
currency, USD values, explorer links, and the node and explorer its
checks ask. explorerUrl(), renderAddressHtml(), getPrice(), formatFee()
and checkEtherscanLabel() take an optional chain id for this. A saved
transaction whose chain id names no network is not restored.

Model: opus-5-5

src/popup/views/helpers.js

@@ -22,6 +22,7 @@ const { resolveTokenSymbol } = require("../../shared/approvalAmount");
 const { DEBUG } = require("../../shared/constants");
 const { escapeHtml } = require("../../shared/html");
 const { isDebug } = require("../../shared/log");
+const { networkByChainId } = require("../../shared/networks");
 const { formatUsd, getPrice } = require("../../shared/prices");
 const { state, saveState, currentNetwork } = require("../../shared/state");
 const { displaySymbol } = require("../../shared/symbolDisplay");
@@ -284,11 +285,12 @@ function unknownableAmount(balance) {
 
 // The active network's native token symbol, `ETH` on mainnet and `SepoliaETH`
 // on Sepolia, as src/shared/networks.js names it. The wallet's balances and
-// the Send and confirmation screens, which send on the active network, label a
-// native amount with this; a transaction already made or requested is labelled
-// by its own chain id, through nativeCurrencyByChainId() in networks.js. The
-// "ETH" that state.selectedToken and txInfo.token hold is the native token's
-// id, not its label, and stays "ETH" on every network.
+// the Send screen, which sends on the active network, label a native amount
+// with this; the confirmation screen, and a transaction already made or
+// requested, label it by the transaction's own chain id, through
+// nativeCurrencyByChainId() in networks.js. The "ETH" that state.selectedToken
+// and txInfo.token hold is the native token's id, not its label, and stays
+// "ETH" on every network.
 function nativeCurrency() {
     return currentNetwork().nativeCurrency;
 }
@@ -307,11 +309,12 @@ function tokenLabel(address) {
 // A network fee in wei as the confirmation and approval screens both show it:
 // the ETH figure through truncateAmountNeverZero() and labelled `symbol`, the
 // native currency of the network the fee is paid on, then its USD value when
-// the ETH price is known. The USD value is of the exact fee, not of the
-// truncated figure.
-function formatFee(wei, symbol) {
+// the ETH price is known on the network with `chainId`, or on the active
+// network when no chain id is given. The USD value is of the exact fee, not of
+// the truncated figure.
+function formatFee(wei, symbol, chainId) {
     const eth = formatEther(wei);
-    const ethPrice = getPrice("ETH");
+    const ethPrice = getPrice("ETH", chainId);
     const usd = ethPrice ? formatUsd(parseFloat(eth) * ethPrice) : "";
     return (
         truncateAmountNeverZero(eth) +
@@ -604,17 +607,19 @@ const EXT_ICON =
     `</svg></span>`;
 
 // Block-explorer URLs. The origin is a per-network constant from
-// src/shared/networks.js; only the path segment is data, and it comes out
-// of explorer JSON (a transaction's from/to, a token's address_hash), which
-// nothing upstream validates as hex. percent-encoding it keeps a segment
-// that contains a slash, a query or a fragment from re-pointing the link
-// somewhere else in the explorer.
-function explorerUrl(kind, value) {
-    return `${currentNetwork().explorerUrl}/${kind}/${encodeURIComponent(value)}`;
+// src/shared/networks.js, the explorer of the network with `chainId`, or of
+// the active network when no chain id is given; only the path segment is
+// data, and it comes out of explorer JSON (a transaction's from/to, a token's
+// address_hash), which nothing upstream validates as hex. percent-encoding it
+// keeps a segment that contains a slash, a query or a fragment from
+// re-pointing the link somewhere else in the explorer.
+function explorerUrl(kind, value, chainId) {
+    const network = chainId ? networkByChainId(chainId) : currentNetwork();
+    return `${network.explorerUrl}/${kind}/${encodeURIComponent(value)}`;
 }
 
-function etherscanAddressUrl(address) {
-    return explorerUrl("address", address);
+function etherscanAddressUrl(address, chainId) {
+    return explorerUrl("address", address, chainId);
 }
 
 // The URL still has to be escaped on the way into href="...": encoding
@@ -680,16 +685,18 @@ function attachCopyHandlers(container) {
 //              with them, and the "at least 32 characters" guarantee has
 //              to survive having no current callers to be a guarantee.
 //   noLink   — if true, omit etherscan link
+//   chainId  — the network whose explorer the link opens; the active
+//              network's when absent
 //
 // After inserting the returned HTML into the DOM, call
 // attachCopyHandlers() on the parent to wire up click-to-copy.
 function renderAddressHtml(address, opts) {
-    const { title, ensName, maxLen, noLink } = opts || {};
+    const { title, ensName, maxLen, noLink, chainId } = opts || {};
     const dot = addressDotHtml(address);
     const displayAddr = maxLen
         ? truncateMiddle(address, Math.max(ADDRESS_MIN_DISPLAY_LEN, maxLen))
         : address;
-    const link = etherscanAddressUrl(address);
+    const link = etherscanAddressUrl(address, chainId);
     const extLink = noLink ? "" : etherscanLinkHtml(link);
 
     let html = "";