Server wasm compatibility (#15)

* add axum sse example

* fix: make the sse axum folder name correct

* feat: add common modules for Axum SSE example

This commit adds supporting modules for the Axum Server-Sent Events (SSE) example:
- Added `counter.rs` with a simple counter router implementation
- Added `jsonrpc_frame_codec.rs` for decoding JSON-RPC frames
- Created a `mod.rs` to expose these modules
- Removed the previous SSE example configuration from Cargo.toml

* refactor: remove main.rs and update Cargo.toml for WASM compatibility

This commit makes two key changes:
1. Removes the main.rs file and make it a example
2. Add a wasi_std_io example

* refactor: simplify WASI I/O handling in example and fmt

Merged AsyncInputStream and AsyncOutputStream into a single WasiFd struct with std_in() and std_out() methods, reducing code duplication and improving clarity of the WASI standard I/O example.

* move examples to root

examples/servers/Cargo.toml

@@ -8,7 +8,7 @@ publish = false
 mcp-server = { path = "../../crates/mcp-server" }
 mcp-core = { path = "../../crates/mcp-core" }
 mcp-macros = { path = "../../crates/mcp-macros" }
-tokio = { version = "1", features = ["full"] }
+tokio = { version = "1", features = ["io-util"] }
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 anyhow = "1.0"
@@ -18,14 +18,26 @@ tracing-appender = "0.2"
 futures = "0.3"
 
 [dev-dependencies]
-axum = { version = "0.8", features = ["macros"] }
+
 tokio-util = { version = "0.7", features = ["io", "codec"]}
 rand = { version = "0.8" }
 
+[target.'cfg(not(target_arch = "wasm32"))'.dev-dependencies]
+axum = { version = "0.8", features = ["macros"] }
+tokio = { version = "1", features = ["full"] }
+
+[target.'cfg(target_arch = "wasm32")'.dev-dependencies]
+tokio = { version = "1", features = ["io-util", "rt", "time", "macros"] }
+wasi = { version = "0.11.0+wasi-snapshot-preview1" }
+
 [[example]]
 name = "counter-server"
 path = "src/counter_server.rs"
 
 [[example]]
 name = "axum"
-path = "src/axum.rs"
+path = "src/axum.rs"
+
+[[example]]
+name = "wasi_std_io"
+path = "src/wasi_std_io.rs"