Method resetFramesForAltScreen

src/ink/ink.tsx:1133–1162

* Seed prev/back frames with full-size BLANK screens (rows×cols of empty * cells, not 0×0). In alt-screen mode, next.screen.height is always * terminalRows; if prev.screen.height is 0 (emptyFrame's default), * log-update sees heightDelta > 0 ('growing') and calls renderFrameSlice, * whos

()

   * matches the physical cursor after ENTER_ALT_SCREEN + CSI H (home).
   */
  private resetFramesForAltScreen(): void {
    const rows = this.terminalRows;
    const cols = this.terminalColumns;
    const blank = (): Frame => ({
      screen: createScreen(cols, rows, this.stylePool, this.charPool, this.hyperlinkPool),
      viewport: {
        width: cols,
        height: rows + 1
      },
      cursor: {
        x: 0,
        y: 0,
        visible: true
      }
    });
	    this.frontFrame = blank();
	    this.backFrame = blank();
	    this.logicalFrontFrame = this.frontFrame;
	    this.logicalBackFrame = this.backFrame;
    this.log.reset();
    this.altScreenPendingRepaintMode = 'none';
    this.altScreenPendingPreviousFrame = undefined;
    // Defense-in-depth: alt-screen skips the cursor preamble anyway (CSI H
    // resets), but a stale displayCursor would be misleading if we later
    // exit to main-screen without an intervening render.
    this.displayCursor = null;
    // Fresh frontFrame is blank rows×cols — blitting from it would copy
    // blanks over content. Next alt-screen frame must full-render.
    this.prevFrameContaminated = true;
  }

  /**
   * Copy the current selection to the clipboard without clearing the