activate() {
    if (!this.#activateAC) {
      this.#activateAC = new AbortController();

      this.element.addEventListener("mousedown", this.#onMouseDown.bind(this), {
        capture: true,
        signal: this.#activateAC.signal,
      });
      this.element.classList.add(CSS_CLASS_GRAB);
    }
  }
Bind a mousedown event to the element to enable grab-detection.