Fix round() API to use string parameter, not options object

The spec defines round() as:
  round(numFractionalDigits, roundingMode)

where roundingMode is a string, not an options object.

Changed all examples from:
  value.round(2, { roundingMode: "floor" })
to:
  value.round(2, "floor")

This matches both the spec and the polyfill implementation.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: jessealama

docs/cookbook.md

@@ -67,7 +67,7 @@ function splitBill(totalAmount, numberOfPeople) {
   const perPerson = total.divide(people);
 
   // Round down to cents for most people
-  const roundedPerPerson = perPerson.round(2, { roundingMode: "floor" });
+  const roundedPerPerson = perPerson.round(2, "floor");
 
   // Last person pays the remainder to ensure exact total
   const lastPersonPays = total.subtract(
@@ -361,21 +361,21 @@ const value = new Decimal("123.456");
 console.log(value.round(2).toString()); // => "123.46"
 
 // Always round up (ceiling)
-console.log(value.round(2, { roundingMode: "ceil" }).toString()); // => "123.46"
+console.log(value.round(2, "ceil").toString()); // => "123.46"
 
 // Always round down (floor)
-console.log(value.round(2, { roundingMode: "floor" }).toString()); // => "123.45"
+console.log(value.round(2, "floor").toString()); // => "123.45"
 
 // Round towards zero (truncate)
-console.log(value.round(2, { roundingMode: "trunc" }).toString()); // => "123.45"
+console.log(value.round(2, "trunc").toString()); // => "123.45"
 
 // Round half away from zero
-console.log(value.round(2, { roundingMode: "halfExpand" }).toString()); // => "123.46"
+console.log(value.round(2, "halfExpand").toString()); // => "123.46"
 
 // Negative number example
 const negative = new Decimal("-123.456");
-console.log(negative.round(2, { roundingMode: "floor" }).toString()); // => "-123.46"
-console.log(negative.round(2, { roundingMode: "ceil" }).toString()); // => "-123.45"
+console.log(negative.round(2, "floor").toString()); // => "-123.46"
+console.log(negative.round(2, "ceil").toString()); // => "-123.45"
 ```
 
 ### Financial rounding

docs/decimal.md

@@ -195,20 +195,20 @@ new Decimal("-123.45").negate().toString(); // => "123.45"
 
 All rounding methods follow IEEE 754-2019 rounding modes.
 
-### **round**(_scale_?: number, _options_?: { roundingMode?: string }) : Decimal
+### **round**(_scale_?: number, _roundingMode_?: string) : Decimal
 
 Rounds to a given number of decimal places.
 
 **Parameters:**
 
 - `scale` (number): Number of decimal places to round to (default: 0)
-- `options.roundingMode` (string): One of "ceil", "floor", "trunc", "halfEven" (default), or "halfExpand"
+- `roundingMode` (string): One of "ceil", "floor", "trunc", "halfEven" (default), or "halfExpand"
 
 ```js
 const d = new Decimal("123.456");
 d.round().toString(); // => "123"
 d.round(2).toString(); // => "123.46"
-d.round(2, { roundingMode: "floor" }).toString(); // => "123.45"
+d.round(2, "floor").toString(); // => "123.45"
 ```
 
 ## Comparison Methods