feat: improve skill quality scores across 4 skills

Ran skills through tessl evaluation tooling and applied targeted
improvements to structure, conciseness, and workflow clarity.

| Skill             | Before | After | Change |
|-------------------|--------|-------|--------|
| defuddle          |  100%  | 100%  |   --   |
| json-canvas       |   83%  | 100%  |  +17%  |
| obsidian-bases    |   83%  | 100%  |  +17%  |
| obsidian-cli      |   94%  | 100%  |   +6%  |
| obsidian-markdown |   71%  |  94%  |  +23%  |

Changes:
- Add structured workflows with validation steps
- Extract verbose reference tables to references/ files (progressive disclosure)
- Remove standard Markdown content Claude already knows (obsidian-markdown)
- Add troubleshooting section for common YAML/formula errors (obsidian-bases)
- Restructure plugin dev section into numbered test cycle (obsidian-cli)
- Condense redundant examples, keep one per pattern

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>