Add natspecs for SelfdestructEthSender and mock

contracts/mixins/SelfdestructEthSender.sol

@@ -2,8 +2,17 @@
 
 pragma solidity ^0.8.25;
 
-
+/**
+ * @title SelfdestructEthSender
+ * @notice A one-time-use contract for cost-effective ETH transfers using the `selfdestruct` mechanism.
+ * @dev Upon construction, this contract verifies EVM compatibility with the Cancun upgrade, specifically
+ * testing for support of transient storage via `tload`. It is intended for single-use, allowing for ETH to
+ * be sent more cheaply by self-destructing and sending its balance to a designated address.
+ */
 abstract contract SelfdestructEthSender {
+    /**
+     * @dev Initializes the contract, verifying compatibility with the Cancun EVM upgrade through transient storage support check.
+     */
     constructor() {
         // tload is done to verify that the EVM is cancun-compatible
         // solhint-disable-next-line no-inline-assembly
@@ -12,6 +21,10 @@ abstract contract SelfdestructEthSender {
         }
     }
 
+    /**
+     * @notice Self-destruct contract, transferring the entire ETH balance of the contract to the specified address.
+     * @param receiver The recipient address of the contract's ETH balance.
+     */
     function stopAndTransferBalance(address payable receiver) external {
         selfdestruct(receiver);
     }

contracts/mocks/SelfdestructEthSenderMock.sol

@@ -4,11 +4,21 @@ pragma solidity ^0.8.25;
 
 import "../mixins/SelfdestructEthSender.sol";
 
+/**
+ * @title SelfdestructEthSenderMock
+ * @notice Mock contract extending SelfdestructEthSender for testing purposes, with added functionality to transfer ETH.
+ */
 contract SelfdestructEthSenderMock is SelfdestructEthSender {
+    /// @notice Indicates that an attempt to transfer ETH has failed.
     error ETHTransferFailed();
 
+    /// @notice Allows the contract to receive ETH.
     receive() external payable {}
 
+    /**
+     * @notice Transfers the contract's entire ETH balance to the specified address.
+     * @param receiver The address to which the contract's ETH balance will be transferred.
+     */
     function transferBalance(address payable receiver) external payable {
         // solhint-disable-next-line avoid-low-level-calls
         (bool success, ) = receiver.call{value: address(this).balance}("");