Remove unused responseWriter struct

Address review feedback to remove dead code.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

host/devserver.go

@@ -1,7 +1,6 @@
 package host
 
 import (
-	"bytes"
 	"compress/gzip"
 	"fmt"
 	"io"
@@ -221,18 +220,3 @@ func (d *DevServer) ListenAndServe(addr string) error {
 	d.logger.Printf("Development server running on http://%s", addr)
 	return http.ListenAndServe(addr, d)
 }
-
-// ResponseWriter wraps http.ResponseWriter to capture the response
-type responseWriter struct {
-	http.ResponseWriter
-	buf        *bytes.Buffer
-	statusCode int
-}
-
-func (rw *responseWriter) WriteHeader(code int) {
-	rw.statusCode = code
-}
-
-func (rw *responseWriter) Write(b []byte) (int, error) {
-	return rw.buf.Write(b)
-}