Add support for running the MCP server over HTTP with Server-Sent Events (SSE) using the MCP Streamable HTTP specification, alongside the existing STDIO transport. New features: - Transport abstraction with Transport interface - HTTP transport with session management - SSE support for server-initiated notifications - CORS security with configurable allowed origins - Optional TLS support - CLI flags for HTTP configuration (--transport, --http-address, etc.) - NixOS module options for HTTP transport The HTTP transport implements: - POST /mcp: JSON-RPC requests with session management - GET /mcp: SSE stream for server notifications - DELETE /mcp: Session termination - Origin validation (localhost-only by default) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>