Phase 2: core converter, live conversion, URL state, highlight interaction

src/lib/format.ts

@@ -0,0 +1,16 @@
+import type { Big } from 'big.js';
+import { FRACTIONAL_DIGITS, INTEGER_DIGITS } from './config';
+
+/**
+ * Format a Big value for display.
+ * Uses FRACTIONAL_DIGITS decimal places (fixed-point).
+ * If INTEGER_DIGITS is set, zero-pads the integer portion to that width.
+ */
+export function formatBig(v: Big): string {
+	const fixed = v.toFixed(FRACTIONAL_DIGITS);
+	if (INTEGER_DIGITS === undefined) return fixed;
+
+	const [intPart, fracPart] = fixed.split('.');
+	const paddedInt = intPart.padStart(INTEGER_DIGITS, '0');
+	return fracPart !== undefined ? `${paddedInt}.${fracPart}` : paddedInt;
+}