- Tag duckduckgo-search skill with fallback_for_toolsets: [web] so it
auto-hides when Firecrawl is available and auto-shows when it isn't
- Add 'Conditional Activation' section to CONTRIBUTING.md with full
spec, semantics, and examples for all 4 frontmatter fields
- Add 'Conditional Activation (Fallback Skills)' section to the user-
facing skills docs with field reference table and practical example
- Update SKILL.md format examples in both docs to show the new fields
Follow-up to PR #785 (conditional skill activation feature).
82113f1f1e