Fix missing crypto/rand import in key_comet.go

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

Author: PaulSnow

cmd/accumulated/run/key_comet.go

@@ -10,6 +10,7 @@ package run
 
 import (
 	"crypto/ed25519"
+	"crypto/rand"
 	"encoding/json"
 	"fmt"
 	"os"