fix: WS upgrade via metrics middleware (realtime), DM names, tap reactions

server/internal/platform/metrics/metrics.go

@@ -3,6 +3,9 @@
 package metrics
 
 import (
+	"bufio"
+	"errors"
+	"net"
 	"net/http"
 	"strconv"
 	"strings"
@@ -82,6 +85,23 @@ func (r *recorder) WriteHeader(code int) {
 	r.ResponseWriter.WriteHeader(code)
 }
 
+// Hijack forwards the WebSocket upgrade to the underlying writer. Without
+// this, wrapping the mux breaks every WebSocket handshake.
+func (r *recorder) Hijack() (net.Conn, *bufio.ReadWriter, error) {
+	hj, ok := r.ResponseWriter.(http.Hijacker)
+	if !ok {
+		return nil, nil, errors.New("metrics: response writer does not support hijacking")
+	}
+	return hj.Hijack()
+}
+
+// Flush forwards periodic flush calls for streaming responses.
+func (r *recorder) Flush() {
+	if f, ok := r.ResponseWriter.(http.Flusher); ok {
+		f.Flush()
+	}
+}
+
 // NormalizePath replaces numeric path segments with a placeholder so that
 // per-route cardinality stays bounded regardless of resource IDs.
 func NormalizePath(p string) string {