feat: Add thousands separator to calculator output

Co-authored-by: aider (gemini/gemini-2.5-pro) <aider@aider.chat>

calculator/calculator.app.js

@@ -194,6 +194,12 @@ function fixFloat(n) {
   return n;
 }
 
+function addSeparators(s) {
+  var parts = s.split(".");
+  parts[0] = parts[0].replace(/\B(?=(\d{3})+(?!\d))/g, "'");
+  return parts.join(".");
+}
+
 function doMath(x, y, operator) {
   x = parseFloat(x);
   y = parseFloat(y);
@@ -258,7 +264,7 @@ function displayOutput(num) {
         if (precision < 0) precision = 0;
         num = toExponential(num, precision).replace("e", "E");
     } else {
-        num = numStr;
+        num = addSeparators(numStr);
     }
     if (num.charAt(0) === '-') {
       num = '- ' + num.substr(1);