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/viewRouter.js

@@ -13,6 +13,7 @@
 // cannot be required outside a browser.
 
 const { RESTORABLE_VIEWS } = require("../shared/restorableViews");
+const { SUPPORTED_CHAIN_IDS } = require("../shared/networks");
 
 // The views this page load has rendered.
 //
@@ -125,13 +126,16 @@ function isRenderableDecoded(value) {
 
 // The pending transaction confirmTx.show() renders: `token` reaches
 // renderAddressHtml() when it is not "ETH", and `from`/`to` reach
-// addressTitle(), makeBlockie() and getLocalWarnings().
+// addressTitle(), makeBlockie() and getLocalWarnings(). `chainId`, which
+// show() fills in when it is absent, picks the network whose explorer the
+// address links open, so it has to name one.
 function isRenderablePendingTx(value) {
     return (
         isRecord(value) &&
         isText(value.token) &&
         isAddressText(value.from) &&
-        isAddressText(value.to)
+        isAddressText(value.to) &&
+        (!value.chainId || SUPPORTED_CHAIN_IDS.has(value.chainId))
     );
 }