fix: a token symbol read off a contract is never stored cut mid-emoji (closes #458)

lookupTokenInfo() cut the symbol at 12 and the name at 64 UTF-16 units,
so an emoji outside the Basic Multilingual Plane could be cut between its
two halves and the half left over stored and shown as U+FFFD. Both are
now cut on code points, as displaySymbol() does. A symbol already stored
broken is not repaired.

Model: opus-5-5

src/shared/balances.js

@@ -334,9 +334,12 @@ async function lookupTokenInfo(contractAddress, rpcUrl, networkId, signal) {
         name = symbol;
     }
 
-    // Truncate to prevent storage of excessively long values from RPC
-    name = String(name).slice(0, 64);
-    symbol = String(symbol).slice(0, 12);
+    // Truncate to prevent storage of excessively long values from RPC.
+    // Counted in code points, as displaySymbol() counts them, so the cut never
+    // falls between the two halves of an emoji and stores a half that renders
+    // as U+FFFD.
+    name = Array.from(String(name)).slice(0, 64).join("");
+    symbol = Array.from(String(symbol)).slice(0, 12).join("");
 
     log.infof("Token resolved:", symbol, "decimals", Number(decimals));
     return { name, symbol, decimals: Number(decimals) };