feat(#132): port MCP (Model Context Protocol) infrastructure

Implement MCP Phase 1 infrastructure for agent tool integration with
central hub, tool registry, and STDIO transport layers.

Components:
- McpHubService: Central registry for MCP server lifecycle
- StdioTransport: STDIO process communication with JSON-RPC 2.0
- ToolRegistryService: Tool catalog management
- McpController: REST API for MCP management

Endpoints:
- GET/POST /mcp/servers - List/register servers
- POST /mcp/servers/:id/start|stop - Lifecycle control
- DELETE /mcp/servers/:id - Unregister
- GET /mcp/tools - List tools
- POST /mcp/tools/:name/invoke - Invoke tool

Features:
- Full JSON-RPC 2.0 protocol support
- Process lifecycle management
- Buffered message parsing
- Type-safe with no explicit any types
- Proper cleanup on shutdown

Tests: 85 passing with 90.9% coverage

Fixes #132

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/api/src/mcp/interfaces/index.ts

@@ -0,0 +1,3 @@
+export * from "./mcp-server.interface";
+export * from "./mcp-tool.interface";
+export * from "./mcp-message.interface";

apps/api/src/mcp/interfaces/mcp-message.interface.ts

@@ -0,0 +1,47 @@
+/**
+ * JSON-RPC 2.0 request message for MCP
+ */
+export interface McpRequest {
+  /** JSON-RPC version */
+  jsonrpc: "2.0";
+
+  /** Request identifier */
+  id: string | number;
+
+  /** Method name to invoke */
+  method: string;
+
+  /** Optional method parameters */
+  params?: unknown;
+}
+
+/**
+ * JSON-RPC 2.0 error object
+ */
+export interface McpError {
+  /** Error code */
+  code: number;
+
+  /** Error message */
+  message: string;
+
+  /** Optional additional error data */
+  data?: unknown;
+}
+
+/**
+ * JSON-RPC 2.0 response message for MCP
+ */
+export interface McpResponse {
+  /** JSON-RPC version */
+  jsonrpc: "2.0";
+
+  /** Request identifier (matches request) */
+  id: string | number;
+
+  /** Result data (present on success) */
+  result?: unknown;
+
+  /** Error object (present on failure) */
+  error?: McpError;
+}

apps/api/src/mcp/interfaces/mcp-server.interface.ts

@@ -0,0 +1,46 @@
+import type { ChildProcess } from "node:child_process";
+
+/**
+ * Configuration for an MCP server instance
+ */
+export interface McpServerConfig {
+  /** Unique identifier for the server */
+  id: string;
+
+  /** Human-readable name for the server */
+  name: string;
+
+  /** Description of what the server provides */
+  description: string;
+
+  /** Command to execute to start the server */
+  command: string;
+
+  /** Optional command-line arguments */
+  args?: string[];
+
+  /** Optional environment variables */
+  env?: Record<string, string>;
+}
+
+/**
+ * Status of an MCP server
+ */
+export type McpServerStatus = "starting" | "running" | "stopped" | "error";
+
+/**
+ * Runtime state of an MCP server
+ */
+export interface McpServer {
+  /** Server configuration */
+  config: McpServerConfig;
+
+  /** Current status */
+  status: McpServerStatus;
+
+  /** Running process (if started) */
+  process?: ChildProcess;
+
+  /** Error message (if in error state) */
+  error?: string;
+}

apps/api/src/mcp/interfaces/mcp-tool.interface.ts

@@ -0,0 +1,16 @@
+/**
+ * MCP tool definition from a server
+ */
+export interface McpTool {
+  /** Tool name (unique identifier) */
+  name: string;
+
+  /** Human-readable description */
+  description: string;
+
+  /** JSON Schema for tool input */
+  inputSchema: object;
+
+  /** ID of the server providing this tool */
+  serverId: string;
+}