feat: recreate remaining missing agent smart contracts from docs

contracts/contracts/KnowledgeGraphMarket.sol

@@ -0,0 +1,58 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.19;
+
+import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
+import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
+import "@openzeppelin/contracts/access/Ownable.sol";
+import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
+
+contract KnowledgeGraphMarket is Ownable, ReentrancyGuard {
+    using SafeERC20 for IERC20;
+
+    IERC20 public aitbcToken;
+    uint256 public graphCounter;
+    uint256 public platformFeePercentage = 250; // 2.5%
+
+    struct KnowledgeGraph {
+        uint256 id;
+        address creator;
+        string cid;
+        uint256 price;
+        uint256 totalSales;
+        bool isActive;
+    }
+
+    mapping(uint256 => KnowledgeGraph) public graphs;
+    mapping(uint256 => mapping(address => bool)) public hasPurchased;
+
+    event GraphListed(uint256 indexed id, address indexed creator, string cid, uint256 price);
+    event GraphPurchased(uint256 indexed id, address indexed buyer, uint256 price);
+
+    constructor(address _aitbcToken) {
+        aitbcToken = IERC20(_aitbcToken);
+    }
+
+    function listGraph(string calldata _cid, uint256 _price) external returns (uint256) {
+        uint256 id = graphCounter++;
+        graphs[id] = KnowledgeGraph(id, msg.sender, _cid, _price, 0, true);
+        emit GraphListed(id, msg.sender, _cid, _price);
+        return id;
+    }
+
+    function purchaseGraph(uint256 _id) external nonReentrant {
+        KnowledgeGraph storage graph = graphs[_id];
+        require(graph.isActive, "Graph inactive");
+        require(!hasPurchased[_id][msg.sender], "Already purchased");
+
+        uint256 fee = (graph.price * platformFeePercentage) / 10000;
+        uint256 creatorAmount = graph.price - fee;
+
+        aitbcToken.safeTransferFrom(msg.sender, address(this), graph.price);
+        aitbcToken.safeTransfer(graph.creator, creatorAmount);
+
+        graph.totalSales++;
+        hasPurchased[_id][msg.sender] = true;
+
+        emit GraphPurchased(_id, msg.sender, graph.price);
+    }
+}