Add streamable HTTP server mode

[syucream]

Summary

• update MCP SDK to ^1.1.0
• add ability to run server either on stdio or streamable HTTP
• support --port command line flag to enable HTTP mode
• document --port flag in README
• fix npm lockfile integrity

Testing

• npm run lint
• npm test

[Copilot]

Pull Request Overview

This PR adds the ability to run the Lightdash MCP Server in streamable HTTP mode using Server-Sent Events (SSE) and provides a CLI flag to enable it, while still supporting the existing stdio mode.

• Upgraded the MCP SDK to ^1.1.0
• Added HTTP mode with SSE endpoint support and corresponding error handling
• Updated README to document the usage of the --port flag

Reviewed Changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 1 comment.

File	Description
src/index.ts	Introduces separate functions for stdio and HTTP modes including SSE transport handling
README.md	Documents the new --port flag for activating the HTTP server mode

Files not reviewed (1)

• package.json: Language not supported

[Copilot]

Using a single 'transport' variable to manage the SSE connection might lead to issues when handling multiple concurrent connections; consider implementing a mechanism (e.g., mapping session IDs to transports) to support multiple clients.

Suggested change

	let transport: SSEServerTransport | undefined;
	app.get('/sse', async (_req, res) => {
	transport = new SSEServerTransport('/message', res);
	await server.connect(transport);
	console.error(
	`Lightdash MCP Server new SSE connection ${transport.sessionId}`
	);
	});
	app.post('/message', async (req, res) => {
	const transports = new Map<string, SSEServerTransport>();
	app.get('/sse', async (_req, res) => {
	const transport = new SSEServerTransport('/message', res);
	transports.set(transport.sessionId, transport);
	await server.connect(transport);
	console.error(
	`Lightdash MCP Server new SSE connection ${transport.sessionId}`
	);
	// Clean up when the connection is closed
	res.on('close', () => {
	transports.delete(transport.sessionId);
	console.error(`SSE connection closed: ${transport.sessionId}`);
	});
	});
	app.post('/message', async (req, res) => {
	const sessionId = req.body.sessionId;
	const transport = transports.get(sessionId);