feat!: extract Axum to standalone rust-mcp-axum crate

[hashemix]

📌 Summary

Extracts the Axum HTTP server integration from rust-mcp-sdk into a standalone
rust-mcp-axum crate. This makes rust-mcp-sdk framework-agnostic (zero HTTP
framework dependencies) while providing a dedicated first-class Axum crate.

👥 Support for both scenarios:

• Turnkey — create_axum_server().start().await
• Bring Your Server — mcp_routes(state, handler, &mount_opts) to mount on existing Axum apps

✨ Changes Made

• New crate: crates/rust-mcp-axum/ - standalone Axum integration with
  AxumServer, AxumServerOptions, AxumRuntime, mcp_routes() mount function,
  AxumMountOptions for BYO-server pattern, and create_axum_server() factory

• Renamed types:

  • HyperServer → AxumServer
  • HyperServerOptions → AxumServerOptions
  • HyperRuntime → AxumRuntime
  • create_server() → create_axum_server()

• Deleted crates/rust-mcp-sdk/src/hyper_servers/ , SDK is now framework-agnostic ⭐

• SDK cleanup: removed axum, axum-server dependencies; removed hyper-server,
  ssl, tls-no-provider features;

• removed #[cfg(feature = "hyper-server")] gates

• Added new tests in covering health check, streamable HTTP, SSE, messages, fallback routes, error bridge, and options

• Updated SDK examples and related SDK integration tests as well as rust-mcp-extra examples

🛠️ Testing Steps

# Full CI pipeline
cargo make check

💡 Additional Notes

Breaking changes :

# Cargo.toml
- rust-mcp-sdk = { features = ["hyper-server"] }
+ rust-mcp-sdk = "0.10"
+ rust-mcp-axum = "0.1"
# source code
- use rust_mcp_sdk::mcp_server::{hyper_server, HyperServerOptions};
- let server = hyper_server::create_server(details, handler, options);
+ use rust_mcp_axum::{create_axum_server, AxumServerOptions};
+ let server = create_axum_server(details, handler, options);