feat(doc-to-markdown): CJK bold spacing, JSON pretty-print, 31 tests, full rename cleanup

- Add CJK bold spacing fix: insert spaces around **bold** spans containing
  CJK characters for correct rendering (handles emoji adjacency, already-spaced)
- Add JSON pretty-print: auto-format JSON code blocks with 2-space indent
- Add 31 unit tests covering all post-processing functions
- Fix pandoc simple table detection (1-space column gaps)
- Fix image path double-nesting when --assets-dir ends with 'media'
- Rename all markdown-tools references across 15 files (README, QUICKSTART,
  marketplace.json, CLAUDE.md, meeting-minutes-taker, GitHub templates)
- Add 5-tool benchmark report (Docling/MarkItDown/Pandoc/Mammoth/ours)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

demos/README.md

@@ -14,7 +14,7 @@ demos/
 │   └── package-skill.tape        # Package for distribution
 ├── github-ops/
 │   └── create-pr.tape            # Create pull requests
-├── markdown-tools/
+├── doc-to-markdown/
 │   └── convert-docs.tape         # Convert documents
 └── generate_all_demos.sh         # Generate all GIFs
 ```