chore: escape every value the views write as markup, and cut symbols on code points (closes #329)

The token screen's decimals and holder count, the ETH price, every address
total and each balance row's USD value went into innerHTML unescaped, against
the rule at the top of src/popup/views/helpers.js. They are escaped now. None
could carry markup, but formatUsd() writes a value under a cent as "< $0.01".

displaySymbol() counts a symbol in code points, not UTF-16 units, so the cut
never leaves half of an emoji, which rendered as U+FFFD.

explorerLink() was already removed on next.

Model: opus-5-5

src/popup/views/addressDetail.js

@@ -66,7 +66,7 @@ function show() {
     $("address-line").dataset.full = addr.address;
     attachCopyHandlers($("address-line"));
     const usdTotal = formatAddressTotal(getAddressValue(addr));
-    $("address-usd-total").innerHTML = usdTotal || " ";
+    $("address-usd-total").innerHTML = escapeHtml(usdTotal) || " ";
     const ensEl = $("address-ens");
     // ENS is now shown inside renderAddressHtml, hide the separate element
     ensEl.classList.add("hidden");

src/popup/views/addressToken.js

@@ -103,7 +103,7 @@ function show() {
     // USD total for this token only
     const usdVal = price && amount !== null ? amount * price : null;
     const usdStr = formatUsd(usdVal);
-    $("address-token-usd-total").innerHTML = usdStr || " ";
+    $("address-token-usd-total").innerHTML = escapeHtml(usdStr) || " ";
 
     // Single token balance line (no tokenId — not clickable here)
     $("address-token-balance").innerHTML = balanceLine(symbol, amount, price);
@@ -148,9 +148,9 @@ function show() {
         if (tokenSymbol)
             infoHtml += `<div class="mb-1"><span class="text-muted">Symbol:</span> ${tokenSymbol}</div>`;
         if (tokenDecimals != null)
-            infoHtml += `<div class="mb-1"><span class="text-muted">Decimals:</span> ${tokenDecimals}</div>`;
+            infoHtml += `<div class="mb-1"><span class="text-muted">Decimals:</span> ${escapeHtml(tokenDecimals)}</div>`;
         if (tokenHolders != null)
-            infoHtml += `<div class="mb-1"><span class="text-muted">Holders:</span> ${Number(tokenHolders).toLocaleString()}</div>`;
+            infoHtml += `<div class="mb-1"><span class="text-muted">Holders:</span> ${escapeHtml(Number(tokenHolders).toLocaleString())}</div>`;
         if (projectUrl)
             infoHtml += `<div class="mb-1"><span class="text-muted">Website:</span> <a href="${escapeHtml(projectUrl)}" target="_blank" rel="noopener" class="underline decoration-dashed">${escapeHtml(projectUrl)}</a></div>`;
         contractInfo.innerHTML = infoHtml;

src/popup/views/helpers.js

@@ -325,7 +325,7 @@ function balanceLine(symbol, amount, price, tokenId) {
     const qty = amount === null ? "quantity unknown" : amount.toFixed(4);
     const usd =
         price && amount !== null
-            ? formatUsd(amount * price) || " "
+            ? escapeHtml(formatUsd(amount * price)) || " "
             : " ";
     // tokenId is a contract address out of the same explorer JSON, and it
     // lands inside a quoted attribute.

src/popup/views/home.js

@@ -63,7 +63,7 @@ function renderTotalValue() {
     const ethPrice = getPrice("ETH");
     if (priceEl) {
         priceEl.innerHTML = ethPrice
-            ? formatUsd(ethPrice) + " USD/ETH"
+            ? escapeHtml(formatUsd(ethPrice) + " USD/ETH")
             : " ";
     }
 
@@ -79,7 +79,8 @@ function renderTotalValue() {
     el.textContent = ethStr + ethUsd;
 
     if (subEl) {
-        subEl.innerHTML = formatAddressTotal(getAddressValue(addr)) || " ";
+        subEl.innerHTML =
+            escapeHtml(formatAddressTotal(getAddressValue(addr))) || " ";
     }
 }
 
@@ -280,7 +281,7 @@ function walletListHtml() {
             }
             html += `<div class="am-address text-xs">${escapeHtml(addr.address)}</div>`;
             const addrTotal = formatAddressTotal(getAddressValue(addr));
-            html += `<div class="text-xs text-muted text-right min-h-[1rem]">${addrTotal || "&nbsp;"}</div>`;
+            html += `<div class="text-xs text-muted text-right min-h-[1rem]">${escapeHtml(addrTotal) || "&nbsp;"}</div>`;
             html += balanceLinesForAddress(
                 addr,
                 state.trackedTokens,

src/shared/symbolDisplay.js

@@ -20,6 +20,10 @@
 // (MSYRUPUSDP), so nothing the wallet ships as a real token is ever
 // truncated. The ellipsis is what tells the user the name they are looking
 // at is not the whole name — worth knowing before they send to it.
+//
+// Characters are counted as code points, not UTF-16 units, so an emoji is
+// one character and the cut never falls between the two halves of one: a
+// half on its own renders as U+FFFD.
 
 const MAX_SYMBOL_LENGTH = 12;
 
@@ -32,8 +36,9 @@ const UNKNOWN_SYMBOL = "???";
 function displaySymbol(symbol) {
     const s = symbol === null || symbol === undefined ? "" : String(symbol);
     if (s.length === 0) return UNKNOWN_SYMBOL;
-    if (s.length <= MAX_SYMBOL_LENGTH) return s;
-    return s.slice(0, MAX_SYMBOL_LENGTH - 1) + "…";
+    const chars = Array.from(s);
+    if (chars.length <= MAX_SYMBOL_LENGTH) return s;
+    return chars.slice(0, MAX_SYMBOL_LENGTH - 1).join("") + "…";
 }
 
 module.exports = {