style(skills): format meta-convert-guide reference tables (#803)

### Changed
- Aligned markdown table columns in difficulty-matrix.md
- Aligned markdown table columns in memory-ownership.md
- Aligned markdown table columns in metaprogramming.md
- Fixed blockquote formatting in referenced-by sections

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Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: aRustyDev