fix: a popup reload mid-refresh no longer logs the requests it cancels (closes #218)

Chrome cancels a closing popup's open requests just after pagehide, and in
the page a cancelled fetch() fails with the same "Failed to fetch" as a
server that cannot be reached. The home screen's transaction list and the
balance refresh logged an error for each, and the e2e suite failed on them.

The popup now aborts an AbortController on pagehide, and those failure
reports check its signal first. End-to-end tests reload the popup with
Blockscout held and require nothing logged, and fail the transaction list
for real and require the failure reported; a unit test covers the balance
refresh. The address and token screens and the new-wallet address scan are
#475.

Model: opus-5-5

tests/e2e/network.js

@@ -418,27 +418,23 @@ function sleep(ms) {
 const HOLD_POLL_MS = 25;
 const HOLD_MAX_MS = 30000;
 
-// Hold a gas estimate open for as long as the test asks.
+// Hold a reply open for as long as the test asks: until opts[name] is false.
 //
-// opts.holdGasEstimate is read here rather than captured, so a test flips it
-// on the same options object the route was registered with — the same
-// pattern as seedTokenTransfer. This is the only way to observe the
-// confirmation screen while its estimate is genuinely in flight; sampling
-// the screen and hoping to win a race against the network would assert
-// nothing on a slow machine.
+// The switch (holdGasEstimate or holdBlockscout) is read here rather than
+// captured, so a test flips it on the same options object the route was
+// registered with — the same pattern as seedTokenTransfer. This is the only way
+// to observe a screen while its request is genuinely in flight; sampling the
+// screen and hoping to win a race against the network would assert nothing on
+// a slow machine.
 //
 // It never gives up quietly. A hold that outlives the bound is reported like
 // any other harness fault, because a "pending" state that stopped being
 // pending on its own is a green assertion about the wrong screen.
-async function awaitRelease(opts, report) {
+async function awaitRelease(opts, name, report) {
     const started = Date.now();
-    while (opts.holdGasEstimate) {
+    while (opts[name]) {
         if (Date.now() - started > HOLD_MAX_MS) {
-            report(
-                "held gas estimate was never released after " +
-                    HOLD_MAX_MS +
-                    "ms",
-            );
+            report(name + " was never released after " + HOLD_MAX_MS + "ms");
             return;
         }
         await sleep(HOLD_POLL_MS);
@@ -562,7 +558,7 @@ async function handleRpc(route, postData, opts, report) {
         return route.abort();
     }
     if (batch.some((req) => req.method === "eth_estimateGas")) {
-        await awaitRelease(opts, report);
+        await awaitRelease(opts, "holdGasEstimate", report);
     }
 
     const replies = batch.map((req) => rpcReply(req, opts, report));
@@ -618,6 +614,10 @@ function traceEnabled(raw) {
  *   node-side refusal.
  * @param {boolean} [opts.holdGasEstimate]  hold every batch containing an
  *   eth_estimateGas until this is cleared again.
+ * @param {boolean} [opts.holdBlockscout]  hold every Blockscout request until
+ *   this is cleared again.
+ * @param {boolean} [opts.failTransactionList]  fail every request for an
+ *   address's transaction list as a network error; read at request time.
  * @param {string[]} [opts.broadcastTransactions]  every raw signed
  *   transaction handed to eth_sendRawTransaction, appended in order.
  * @param {number|string|null} [opts.tokenDecimalsOverride]  the scale
@@ -693,7 +693,12 @@ async function installNetworkStubs(ctx, opts) {
 
         // Blockscout v2
         if (p.includes("/api/v2/")) {
+            await awaitRelease(opts, "holdBlockscout", report);
             if (/\/addresses\/0x[0-9a-fA-F]{40}\/transactions$/.test(p)) {
+                // Aborted rather than answered with an error status: to the
+                // page this is a server that cannot be reached, and fetch()
+                // rejects with "Failed to fetch".
+                if (opts.failTransactionList) return route.abort();
                 const addr = blockscoutAddress(p);
                 return jsonResponse(route, {
                     items: