Update README with WireframeProtocol integration

README.md

@@ -133,16 +133,56 @@ let app = WireframeApp::new()?
 
 ## Connection Lifecycle
 
-`WireframeApp` can run callbacks when a connection is opened or closed. The
-state produced by `on_connection_setup` is passed to `on_connection_teardown`
-when the connection ends.
+Protocol callbacks are consolidated under the `WireframeProtocol` trait,
+replacing the individual `on_connection_setup`/`on_connection_teardown`
+closures. The trait methods are synchronous so the trait remains object safe,
+but callbacks can spawn asynchronous tasks when needed. A protocol
+implementation registers hooks for connection setup, frame mutation and command
+completion. The associated `ProtocolError` type is used by other parts of the
+API, such as request handling.
 
 ```rust
-    let app = WireframeApp::new()
-        .on_connection_setup(|| async { 42u32 })
-        .on_connection_teardown(|state| async move {
-            println!("closing with {state}");
+pub trait WireframeProtocol: Send + Sync + 'static {
+    type Frame: FrameLike;
+    type ProtocolError;
+
+    fn on_connection_setup(
+        &self,
+        handle: PushHandle<Self::Frame>,
+        ctx: &mut ConnectionContext,
+    );
+
+    fn before_send(&self, frame: &mut Self::Frame, ctx: &mut ConnectionContext);
+
+    fn on_command_end(&self, ctx: &mut ConnectionContext);
+}
+
+struct MySqlProtocolImpl;
+
+impl WireframeProtocol for MySqlProtocolImpl {
+    type Frame = Vec<u8>;
+    type ProtocolError = ();
+
+    fn on_connection_setup(
+        &self,
+        handle: PushHandle<Self::Frame>,
+        _ctx: &mut ConnectionContext,
+    ) {
+        // Spawn an async task to send a heartbeat after setup
+        tokio::spawn(async move {
+            let _ = handle.push_high_priority(b"ping".to_vec()).await;
         });
+    }
+
+    fn before_send(&self, _frame: &mut Self::Frame, _ctx: &mut ConnectionContext) {}
+
+    fn on_command_end(&self, _ctx: &mut ConnectionContext) {}
+}
+
+```
+
+```rust
+let app = WireframeApp::new().with_protocol(MySqlProtocolImpl);
 ```
 
 ## Custom Extractors