Method shiftSelectionForScroll

src/ink/ink.tsx:1168–1178

* Shift anchor AND focus by dRow, clamped to [minRow, maxRow]. Used by * keyboard scroll handlers (PgUp/PgDn etc.) so the highlight tracks the * content instead of disappearing. Unlike shiftAnchor (drag-to-scroll), * this moves BOTH endpoints — the user isn't holding the mouse at one * e

(dRow: number, minRow: number, maxRow: number)

   * edge. Supplies screen.width for the col-reset-on-clamp boundary.
   */
  shiftSelectionForScroll(dRow: number, minRow: number, maxRow: number): void {
    const hadSel = hasSelection(this.selection);
    shiftSelection(this.selection, dRow, minRow, maxRow, this.frontFrame.screen.width);
    // shiftSelection clears when both endpoints overshoot the same edge
    // (Home/g/End/G page-jump past the selection). Notify subscribers so
    // useHasSelection updates. Safe to call notifySelectionChange here —
    // this runs from keyboard handlers, not inside onRender().
    if (hadSel && !hasSelection(this.selection)) {
      this.notifySelectionChange();
    }
  }

  /**
   * Keyboard selection extension (shift+arrow/home/end). Moves focus;