feat: implement MCP proxy for OpenClaw tool access in contractor agent

Complete the MCP tool call chain:
- contractor-agent bridge exposes /mcp/execute endpoint for tool callbacks
- openclaw-mcp-server.mjs proxies OpenClaw tool defs to Claude as MCP tools
- sdk-adapter passes --mcp-config on first turn with all OpenClaw tools
- tool-test plugin registers contractor_echo in globalThis tool handler map
- agent-config-writer auto-sets tools.profile=full so OpenClaw sends tool defs
- Fix --mcp-config arg ordering: prompt must come before <configs...> flag

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/contractor/runtime-state.ts

@@ -0,0 +1,15 @@
+import path from "node:path";
+import fs from "node:fs";
+
+export function getContractorStateDir(workspace: string): string {
+  return path.join(workspace, ".openclaw", "contractor-agent");
+}
+
+export function getSessionMapPath(workspace: string): string {
+  return path.join(getContractorStateDir(workspace), "session-map.json");
+}
+
+export function ensureContractorStateDir(workspace: string): void {
+  const dir = getContractorStateDir(workspace);
+  fs.mkdirSync(dir, { recursive: true });
+}