feat: Take reactor address as input to UniswapXFiller

- Put reactor zero address check in separate line for more easy debugging.
- Also includes other small cosmetic changes.

foundry/src/uniswap_x/IStructs.sol

@@ -3,7 +3,6 @@ pragma solidity ^0.8.26;
 
 /// @dev external struct including a generic encoded order and swapper signature
 ///  The order bytes will be parsed and mapped to a ResolvedOrder in the concrete reactor contract
-
 struct SignedOrder {
     bytes order;
     bytes sig;
@@ -41,8 +40,8 @@ struct OutputToken {
     uint256 amount;
     address recipient;
 }
-/// @dev generic concrete order that specifies exact tokens which need to be sent and received
 
+/// @dev generic concrete order that specifies exact tokens which need to be sent and received
 struct ResolvedOrder {
     OrderInfo info;
     InputToken input;

foundry/src/uniswap_x/UniswapXFiller.sol

@@ -16,8 +16,7 @@ contract UniswapXFiller is AccessControl, IReactorCallback {
     using SafeERC20 for IERC20;
 
     // UniswapX V2DutchOrder Reactor
-    IReactor public constant USXEDAReactor =
-        IReactor(0x00000011F84B9aa48e5f8aA8B9897600006289Be);
+    IReactor public immutable USXEDAReactor;
     address public immutable tychoRouter;
 
     // keccak256("NAME_OF_ROLE") : save gas on deployment
@@ -30,12 +29,14 @@ contract UniswapXFiller is AccessControl, IReactorCallback {
         address indexed token, uint256 amount, address indexed receiver
     );
 
-    constructor(address _tychoRouter) {
+    constructor(address _tychoRouter, address _reactor) {
         if (_tychoRouter == address(0)) revert UniswapXFiller__AddressZero();
+        if (_reactor == address(0)) revert UniswapXFiller__AddressZero();
 
         _grantRole(DEFAULT_ADMIN_ROLE, msg.sender);
         _grantRole(REACTOR_ROLE, address(USXEDAReactor));
         tychoRouter = _tychoRouter;
+        USXEDAReactor = IReactor(_reactor);
     }
 
     function execute(SignedOrder calldata order, bytes calldata callbackData)
@@ -65,7 +66,7 @@ contract UniswapXFiller is AccessControl, IReactorCallback {
     }
 
     /**
-     * @dev Allows withdrawing any ERC20 funds if funds get stuck in case of a bug.
+     * @dev Allows withdrawing any ERC20 funds.
      */
     function withdraw(IERC20[] memory tokens, address receiver)
         external
@@ -84,8 +85,7 @@ contract UniswapXFiller is AccessControl, IReactorCallback {
     }
 
     /**
-     * @dev Allows withdrawing any NATIVE funds if funds get stuck in case of a bug.
-     * The contract should never hold any NATIVE tokens for security reasons.
+     * @dev Allows withdrawing any NATIVE funds.
      */
     function withdrawNative(address receiver)
         external