feat: add MCP server skeleton

TASKS.md

@@ -406,3 +406,38 @@ All five tool handlers are implemented and tested:
 ---
 
 Phase 2 complete. Phase 3 complete. Phase 4 complete. Phase 5 next: MCP Server and Tool Registration.
+
+---
+
+## Phase 5 - MCP Server and Tool Registration
+
+### Task 5.1 - MCP server skeleton
+
+Create the minimal runnable MCP server in `src/server.js`.
+
+**Requirements:**
+- Use `McpServer` from `@modelcontextprotocol/sdk/server/mcp.js`.
+- Use `StdioServerTransport` from `@modelcontextprotocol/sdk/server/stdio.js`.
+- Create server with name `"chatgpt-mcp"` and version `"0.1.0"`.
+- Connect over stdio transport.
+- Register no tools yet.
+- Import no tool handlers yet.
+- Do not load config.
+- Do not call OpenAI.
+- Keep it minimal (~15 lines).
+
+**Smoke test:**
+```bash
+printf '%s\n' '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"smoke-test","version":"0.0.1"}}}' | npm start
+```
+
+Expected: process starts, no import/runtime crash, MCP initialize response returned with correct `serverInfo.name` and `serverInfo.version`.
+
+Status: ✅ Complete
+
+**What Task 5.1 established:**
+- MCP stdio server skeleton is operational.
+- MCP initialize handshake succeeds.
+- No tools registered yet — that belongs to Task 5.2.
+
+### Task 5.2 - Register ask_chatgpt MCP tool (NEXT)