Fix refund amount validation to prevent exceeding order total

The "Invalid refund amount" error occurred because calculated refund amounts slightly exceeded the available order total due to rounding errors in tax calculations.

Changes:
- Calculate maximum refundable amount (order total - already refunded)
- Cap refund amount to maximum available before calling wc_create_refund()
- Round both calculated refund and max refund to 2 decimal places
- Improve error logging to show order total and already refunded amounts

Example of the issue:
- Order total: $24851.03
- Calculated refund (with 3 decimal tax): $24851.04
- Result: $0.01 over limit → "Invalid refund amount" error

This fix ensures refunds never exceed the mathematically available amount, preventing WooCommerce validation errors.

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

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

Author: layoutd

includes/Generator/Order.php

@@ -521,13 +521,26 @@ protected static function create_refund( $order, $force_partial = false ) {
 			}
 		}
 
+		// Round refund amount to 2 decimal places for currency precision
+		$refund_amount = round( $refund_amount, 2 );
+
+		// Calculate maximum refundable amount (order total minus already refunded)
+		$max_refund = $order->get_total() - $order->get_total_refunded();
+		$max_refund = round( $max_refund, 2 );
+
+		// Cap refund amount to maximum available (prevents rounding errors from exceeding order total)
+		if ( $refund_amount > $max_refund ) {
+			$refund_amount = $max_refund;
+		}
+
 		// Validate refund amount is greater than 0
 		if ( $refund_amount <= 0 ) {
 			error_log( sprintf(
-				'Refund skipped for order %d: Invalid refund amount (%s). Order total: %s',
+				'Refund skipped for order %d: Invalid refund amount (%s). Order total: %s, Already refunded: %s',
 				$order->get_id(),
 				$refund_amount,
-				$order->get_total()
+				$order->get_total(),
+				$order->get_total_refunded()
 			) );
 			return false;
 		}
@@ -556,10 +569,12 @@ protected static function create_refund( $order, $force_partial = false ) {
 		);
 		if ( is_wp_error( $refund ) ) {
 			error_log( sprintf(
-				"Refund creation failed for order %d:\nError: %s\nAmount: %s\nReason: %s\nLine Items: %s",
+				"Refund creation failed for order %d:\nError: %s\nCalculated Amount: %s\nOrder Total: %s\nOrder Refunded Total: %s\nReason: %s\nLine Items: %s",
 				$order->get_id(),
 				$refund->get_error_message(),
 				$refund_amount,
+				$order->get_total(),
+				$order->get_total_refunded(),
 				$reason,
 				print_r( $line_items, true )
 			) );