Incorrect textContent Output for <pre><code> Blocks

[zuisong]

Description

When using happy-dom to parse HTML containing a <pre><code> block, the output of document.body.textContent is duplicated and incorrect. The expected output should match the original content inside the <code> tag, but the actual output contains repeated and misplaced lines.

Steps to Reproduce

1. Run the following code:

   import { Window } from "happy-dom";
   
   const w = new Window();
   const document = w.document;
   document.body.innerHTML = `<pre v-pre data-lang="svgbob"><code class="lang-svgbob">                  .-,(  ),-.
      ___  _      .-(          )-.
     [___]|=| -->(                )      __________
     /::/ |_|     '-(          ).-' --->[_...__... ]
                     '-.( ).-'
                             \      ____   __
                              '--->|    | |==|
                                   |____| |  |
                                   /::::/ |__|</code></pre>`;
   console.log(document.body.textContent);

2. Observe the output.

Actual Output

                  .-,(  ),-.
   ___  _      .-(          )-.
  [___]|=|                   .-,(  ),-.
   ___  _      .-(          )-.
  [___]|=| -->(                )      __________
  /::/ |_|     '-(          ).-' -(                )      __________
  /::/ |_|     '-(          ).-' --->[_...__... ]
                  '-.( ).-'
                                ____   __
                           '-[_...__... ]
                  '-.( ).-'
                                ____   __
                           '--->|    | |==|
                                |____| |  |
                                /::::/ |__|

Expected Output

                  .-,(  ),-.
   ___  _      .-(          )-.
  [___]|=| -->(                )      __________
  /::/ |_|     '-(          ).-' --->[_...__... ]
                  '-.( ).-'
                          \      ____   __
                           '--->|    | |==|
                                |____| |  |
                                /::::/ |__|

Screenshots

Environment

• happy-dom version: 17.5.6
• Node.js version: 23.11.0
• OS: macOS