ScriptKit v1.3.0: fix code block markdown isolation, null topic guard

- Fix: code/pre blocks no longer have content processed as markdown
  (asterisks and [link](url) inside backticks are preserved via placeholder
  extraction + entity encoding for Roll20 chat compatibility)
- Fix: null topic entries no longer crash man command
- html.table: overflow-x:auto wrapper for horizontal scrolling
- Updated registration log format
- Updated README, TODO, version header, changelog