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/mcp.controller.ts

@@ -0,0 +1,118 @@
+import {
+  Controller,
+  Get,
+  Post,
+  Delete,
+  Param,
+  Body,
+  NotFoundException,
+  BadRequestException,
+} from "@nestjs/common";
+import { McpHubService } from "./mcp-hub.service";
+import { ToolRegistryService } from "./tool-registry.service";
+import { RegisterServerDto } from "./dto";
+import type { McpServer, McpTool } from "./interfaces";
+
+/**
+ * Controller for MCP server and tool management
+ */
+@Controller("mcp")
+export class McpController {
+  constructor(
+    private readonly mcpHub: McpHubService,
+    private readonly toolRegistry: ToolRegistryService
+  ) {}
+
+  /**
+   * List all registered MCP servers
+   */
+  @Get("servers")
+  listServers(): McpServer[] {
+    return this.mcpHub.listServers();
+  }
+
+  /**
+   * Register a new MCP server
+   */
+  @Post("servers")
+  async registerServer(@Body() dto: RegisterServerDto): Promise<void> {
+    await this.mcpHub.registerServer(dto);
+  }
+
+  /**
+   * Start an MCP server
+   */
+  @Post("servers/:id/start")
+  async startServer(@Param("id") id: string): Promise<void> {
+    await this.mcpHub.startServer(id);
+  }
+
+  /**
+   * Stop an MCP server
+   */
+  @Post("servers/:id/stop")
+  async stopServer(@Param("id") id: string): Promise<void> {
+    await this.mcpHub.stopServer(id);
+  }
+
+  /**
+   * Unregister an MCP server
+   */
+  @Delete("servers/:id")
+  async unregisterServer(@Param("id") id: string): Promise<void> {
+    const server = this.mcpHub.getServerStatus(id);
+    if (!server) {
+      throw new NotFoundException(`Server ${id} not found`);
+    }
+
+    await this.mcpHub.unregisterServer(id);
+  }
+
+  /**
+   * List all available tools
+   */
+  @Get("tools")
+  listTools(): McpTool[] {
+    return this.toolRegistry.listTools();
+  }
+
+  /**
+   * Get a specific tool by name
+   */
+  @Get("tools/:name")
+  getTool(@Param("name") name: string): McpTool {
+    const tool = this.toolRegistry.getTool(name);
+    if (!tool) {
+      throw new NotFoundException(`Tool ${name} not found`);
+    }
+    return tool;
+  }
+
+  /**
+   * Invoke a tool
+   */
+  @Post("tools/:name/invoke")
+  async invokeTool(@Param("name") name: string, @Body() input: unknown): Promise<unknown> {
+    const tool = this.toolRegistry.getTool(name);
+    if (!tool) {
+      throw new NotFoundException(`Tool ${name} not found`);
+    }
+
+    const requestId = Math.floor(Math.random() * 1000000);
+    const response = await this.mcpHub.sendRequest(tool.serverId, {
+      jsonrpc: "2.0",
+      id: requestId,
+      method: "tools/call",
+      params: {
+        name: tool.name,
+        arguments: input,
+      },
+    });
+
+    if (response.error) {
+      throw new BadRequestException(response.error.message);
+    }
+
+    return response.result;
+  }
+}