feat: add stateless streamable http mode (#8)

[PeterRodenkirchAA]

Related Issue: #8

Why?

The overhead of a stateful streamable HTTP mode might not be necessary for a lot of use cases that submit a simple code execution task via POST request.
We observed some issue with the stateful mode concerning pending GET requests and supporting a stateless mode would simplify the MCP server integration.

What?

• New mode: streamable_http_stateless

  • Stateless per-request handling: a new MCP server and transport are created for each POST /mcp.
  • GET /mcp and DELETE /mcp return 405 -> server-to-client notifications are not supported.
  • The stateful mode is unaffected

• CLI and Python API

  • adds streamable-http-stateless as a mode:
    • uvx mcp-run-python streamable-http-stateless --port 3001

• TypeScript part:

  • runStreamableHttp delegates to:
    • createStatefulHttpServer(...)
    • createStatelessHttpServer(...)
  • Refactored path matching into shared helpers:
    • createPathMatcher(req, url) and pathMatch(req, url)

Usage

• Stateful:

uvx mcp-run-python streamable-http --port 3001

• Stateless:

uvx mcp-run-python streamable-http-stateless --port 3001