Rename module, add features, fix round-trip fidelity

- Rename module to sourcecraft.dev/bigbes/confluence-md-utilities
- Add fmt command with syntax highlighting (--color=auto/force/disabled)
- Add shell completions for all commands with file extension hints
- Preserve ac:layout/ac:layout-section/ac:layout-cell through round-trips
- Preserve ac:macro-id on code blocks and TOC macros
- Preserve table class/style attributes and colgroup column widths
- Preserve TOC macro as <!-- ac:toc --> comment
- Fix table cell rendering to preserve bold, italic, code, br, links
- Fix user references (ri:userkey) and attachment images (ri:attachment)
- Fix inline spacing between formatting elements in list items

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