docs: clean up stale create_session usage instructions in comments and markdown examples

.agents/skills/multi-agent-mux-create/scripts/create_session.sh

@@ -1,7 +1,7 @@
 #!/usr/bin/env bash
 # create_session.sh — multi-agent-mux-create 의 부속 스크립트
 # Usage:
-#   bash create_session.sh --workspace <path> --agent <claude|agy> [--session <name>] [--wrapper]
+#   bash create_session.sh --workspace <path> --agent <claude|agy> --role <role> [--session <name>] [--wrapper]
 #
 # 동작:
 #   1) preflight: tmux/claude/agy 가용성, workspace 존재