feat: recreate remaining missing agent smart contracts from docs

contracts/contracts/AgentCommunication.sol

@@ -0,0 +1,26 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.19;
+
+import "@openzeppelin/contracts/access/Ownable.sol";
+
+contract AgentCommunication is Ownable {
+    struct Message {
+        address sender;
+        address recipient;
+        string encryptedContent;
+        uint256 timestamp;
+    }
+
+    mapping(address => Message[]) public inbox;
+
+    event MessageSent(address indexed sender, address indexed recipient);
+
+    function sendMessage(address _recipient, string calldata _encryptedContent) external {
+        inbox[_recipient].push(Message(msg.sender, _recipient, _encryptedContent, block.timestamp));
+        emit MessageSent(msg.sender, _recipient);
+    }
+
+    function getMessages() external view returns (Message[] memory) {
+        return inbox[msg.sender];
+    }
+}