Add optional AgentV toolset docs and templates

[smota]

Parent epic: #18

Goal

Create optional AgentV toolset documentation and templates under toolsets/agentv/.

Context to preserve

AgentV should be optional, local-first, Git-backed, and adopter-owned. metaskills should provide reusable guidance/templates, not become an eval runtime or hosted platform.

Proposed files

toolsets/agentv/
  README.md
  templates/
    providers.yaml
    eval.eval.yaml
    github-actions-agentv.yml
  examples/
    skill-eval.eval.yaml
    agent-eval.eval.yaml

Content requirements

• Explain when to use AgentV with MetaSkills assets.
• Install/run quickstart:
  • npm install -g agentv
  • agentv init
  • agentv eval ./evals/<asset>.eval.yaml
• Mention supported target families: Pi, Codex, Claude Code, Copilot, OpenCode, direct LLM providers.
• Keep secrets out of repo; use .env.example guidance only.
• Explain result bundle location: .agentv/results/<run_id>/.

Acceptance criteria

• toolsets/agentv/README.md exists and follows repo contribution standards.
• At least one skill eval and one agent eval example exist.
• Template files are clearly marked as optional adopter assets.
• README lists minimal validation command.