SingleFile CLI 2.15.8

CLI fixes and improvements

• single-file-core is updated to 1.6.13, see https://github.com/gildas-lormeau/single-file-core/releases/tag/v1.6.12 and https://github.com/gildas-lormeau/single-file-core/releases/tag/v1.6.13. For the CLI it means the following
• A page with invalid nesting could be saved with some elements moved to the end of their parent when --compress-html is enabled (the default), e.g. the input field of a Google Gemini chat was displayed at the top instead of the bottom (SingleFile#2000). Regression in 2.15.5 (core 1.6.10)
• A link nested in a link, such as on a Substack home page, stayed split in the saved page
• Elements the HTML parser drops when the saved page is opened, such as a <form> inside a <form> or a table cell outside a table, are now kept
• Invalid nesting inside shadow roots is now repaired
• Saving a saved page again added a backslash before each /> in <style> and <script> elements. On Google Gemini, this made the "○" list markers disappear
• Saving a saved page again no longer moves the <meta name=referrer> element

Co-authored by Claude (Claude Code)