fix: never collapse warning container — always reserve space to prevent layout shift

Replace display:none with persistent visibility:hidden so the warning
area occupies the same vertical space regardless of API result.
This eliminates the layout shift that occurred when the container was
collapsed after the recipient history check returned.

src/popup/index.html

@@ -577,6 +577,19 @@
                     <div id="confirm-fee-amount" class="text-xs"></div>
                 </div>
                 <div id="confirm-warnings" class="mb-2 hidden"></div>
+                <div
+                    id="confirm-recipient-warning"
+                    class="mb-2"
+                    style="visibility: hidden"
+                >
+                    <div
+                        class="border border-red-500 border-dashed p-2 text-xs font-bold text-red-500"
+                    >
+                        WARNING: The recipient address has ZERO transaction
+                        history. This may indicate a fresh or unused address.
+                        Double-check the address before sending.
+                    </div>
+                </div>
                 <div
                     id="confirm-errors"
                     class="mb-2 border border-border border-dashed p-2 hidden"

src/popup/views/confirmTx.js

@@ -86,42 +86,6 @@ function valueWithUsd(text, usdAmount) {
     return text;
 }
 
-function renderWarnings(warnings) {
-    const warningsEl = $("confirm-warnings");
-    if (warnings.length > 0) {
-        warningsEl.innerHTML = warnings
-            .map(
-                (w) =>
-                    `<div class="border border-border border-dashed p-2 mb-1 text-xs font-bold" style="color:#c00">WARNING: ${w}</div>`,
-            )
-            .join("");
-        warningsEl.classList.remove("hidden");
-    } else {
-        warningsEl.classList.add("hidden");
-    }
-}
-
-async function checkAddressHistory(address, existingWarnings) {
-    try {
-        const provider = getProvider(state.rpcUrl);
-        const [balance, txCount] = await Promise.all([
-            provider.getBalance(address),
-            provider.getTransactionCount(address),
-        ]);
-        if (balance === 0n && txCount === 0) {
-            const warnings = existingWarnings.slice();
-            warnings.push(
-                "This address has ZERO transaction history. " +
-                    "It has never sent or received funds. " +
-                    "Double-check that the address is correct before sending.",
-            );
-            renderWarnings(warnings);
-        }
-    } catch (e) {
-        log.errorf("address history check failed:", e.message);
-    }
-}
-
 function show(txInfo) {
     pendingTx = txInfo;
 
@@ -212,10 +176,18 @@ function show(txInfo) {
         warnings.push("You are sending to your own address.");
     }
 
-    renderWarnings(warnings);
-
-    // Async check: warn if destination address has zero transaction history
-    checkAddressHistory(txInfo.to, warnings);
+    const warningsEl = $("confirm-warnings");
+    if (warnings.length > 0) {
+        warningsEl.innerHTML = warnings
+            .map(
+                (w) =>
+                    `<div class="border border-border border-dashed p-2 mb-1 text-xs font-bold">WARNING: ${w}</div>`,
+            )
+            .join("");
+        warningsEl.classList.remove("hidden");
+    } else {
+        warningsEl.classList.add("hidden");
+    }
 
     // Check for errors
     const errors = [];
@@ -271,7 +243,13 @@ function show(txInfo) {
     state.viewData = { pendingTx: txInfo };
     showView("confirm-tx");
 
+    // Reset recipient warning: reserve space (visibility:hidden) while
+    // the async check runs, preventing layout shift per README policy.
+    const recipientWarning = $("confirm-recipient-warning");
+    recipientWarning.style.visibility = "hidden";
+
     estimateGas(txInfo);
+    checkRecipientHistory(txInfo);
 }
 
 async function estimateGas(txInfo) {
@@ -314,6 +292,30 @@ async function estimateGas(txInfo) {
     }
 }
 
+async function checkRecipientHistory(txInfo) {
+    const el = $("confirm-recipient-warning");
+    try {
+        const provider = getProvider(state.rpcUrl);
+        // Skip warning for contract addresses — they may legitimately
+        // have zero outgoing transactions (getTransactionCount returns
+        // the nonce, i.e. sent-tx count only).
+        const code = await provider.getCode(txInfo.to);
+        if (code && code !== "0x") {
+            // Contract address — no warning needed, keep space reserved
+            // but invisible to prevent layout shift
+            return;
+        }
+        const txCount = await provider.getTransactionCount(txInfo.to);
+        if (txCount === 0) {
+            el.style.visibility = "visible";
+        }
+        // If txCount > 0, leave visibility:hidden — space stays reserved
+    } catch (e) {
+        log.errorf("recipient history check failed:", e.message);
+        // On error, leave visibility:hidden — no layout shift, no false warning
+    }
+}
+
 function init(ctx) {
     $("btn-confirm-send").addEventListener("click", async () => {
         const password = $("confirm-tx-password").value;

src/popup/views/transactionDetail.js

@@ -158,8 +158,9 @@ function render() {
         loadCalldata(tx.hash, tx.to);
     }
 
-    $("tx-detail-time").textContent =
-        isoDate(tx.timestamp) + " (" + timeAgo(tx.timestamp) + ")";
+    const isoStr = isoDate(tx.timestamp);
+    $("tx-detail-time").innerHTML =
+        copyableHtml(isoStr) + " (" + escapeHtml(timeAgo(tx.timestamp)) + ")";
     $("tx-detail-status").textContent = tx.isError ? "Failed" : "Success";
     showView("transaction");
 

src/popup/views/txStatus.js

@@ -59,6 +59,16 @@ function txHashHtml(hash) {
     );
 }
 
+function blockNumberHtml(blockNumber) {
+    const num = String(blockNumber);
+    const link = `https://etherscan.io/block/${num}`;
+    const extLink = `<a href="${link}" target="_blank" rel="noopener" class="inline-flex items-center">${EXT_ICON}</a>`;
+    return (
+        `<span class="underline decoration-dashed cursor-pointer" data-copy="${escapeHtml(num)}">${escapeHtml(num)}</span>` +
+        extLink
+    );
+}
+
 function attachCopyHandlers(viewId) {
     document
         .getElementById(viewId)
@@ -189,7 +199,7 @@ function renderSuccess() {
         $("success-tx-to").innerHTML = toAddressHtml(d.to);
     }
 
-    $("success-tx-block").textContent = String(d.blockNumber);
+    $("success-tx-block").innerHTML = blockNumberHtml(d.blockNumber);
     $("success-tx-hash").innerHTML = txHashHtml(d.hash);
 
     // Show decoded calldata details if present