SingleFile CLI 2.15.6

CLI fixes and improvements

• single-file-core is updated to 1.6.11, see https://github.com/gildas-lormeau/single-file-core/releases/tag/v1.6.11. It fixes a regression of 1.6.10: a page holding a link nested in a link, such as a Substack home page, failed to save with HierarchyRequestError: Failed to execute 'insertBefore' on 'Node': The new child element contains the parent

Co-authored by Claude (Claude Code)