* docs: add Agent Capabilities overview page and improve Skills docs
- New 'Agent Capabilities' page explaining all 5 extension types (Tools, MCPs, Apps, Skills, Knowledge) with comparison table and decision guide
- Rewrite Skills page with practical examples showing Skills + Tools patterns, common FAQ, and Skills vs Knowledge comparison
- Add cross-reference callout on Tools page linking to the capabilities overview
- Add agent-capabilities to Core Concepts navigation (after agents)
* docs: add pt-BR and ko translations for agent-capabilities and updated skills/tools
* docs: add Arabic (ar) translations for agent-capabilities and updated skills/tools
introduce the agent skills standard for packaging reusable instructions that agents can discover and activate at runtime.
- skills defined via SKILL.md with yaml frontmatter and markdown body
- three-level progressive disclosure: metadata, instructions, resources
- filesystem discovery with directory name validation
- skill lifecycle events (discovery, loaded, activated, failed)
- crew-level skills resolved once and shared across agents
- skill context injected into both task execution and standalone kickoff
