Method handleSelectionDrag

src/ink/ink.tsx:1501–1510

* Handle a drag-motion at (col, row). In char mode updates focus to the * exact cell. In word/line mode snaps to word/line boundaries so the * selection extends by word/line like native macOS. Gated on * altScreenActive for the same reason as dispatchClick.

(col: number, row: number)

   * altScreenActive for the same reason as dispatchClick.
   */
  handleSelectionDrag(col: number, row: number): void {
    if (!this.altScreenActive) return;
    const sel = this.selection;
    if (sel.anchorSpan) {
      extendSelection(sel, this.frontFrame.screen, col, row);
    } else {
      updateSelection(sel, col, row);
    }
    this.notifySelectionChange();
  }

  // Methods to properly suspend stdin for external editor usage
  // This is needed to prevent Ink from swallowing keystrokes when an external editor is active