feat(skill-development): add examples directory with skill templates

[sjnims]

Summary

The skill-development skill is the only skill in plugin-dev without an examples/ directory. The skill teaches "Provide working examples" in its best practices but doesn't follow its own guidance.

Problem

All other plugin-dev skills have examples/:

• ✅ agent-development: examples/
• ✅ command-development: examples/
• ✅ hook-development: examples/
• ✅ mcp-integration: examples/
• ✅ plugin-settings: examples/
• ✅ plugin-structure: examples/
• ❌ skill-development: NO examples/

This inconsistency means:

1. Users can't copy working skill templates
2. The skill doesn't "practice what it preaches"
3. New skill creators have to piece together examples from other skills

Proposed Solution

Create plugins/plugin-dev/skills/skill-development/examples/ with:

1. minimal-skill/SKILL.md

Bare minimum valid skill showing required structure:

---
name: example-minimal
description: This skill should be used when the user asks to "do X" or "perform Y". Demonstrates minimal skill structure.
---

# Example Minimal Skill

Brief description of what this skill provides.

## Instructions

Core instructions go here.

2. complete-skill/ directory

Full structure demonstrating all components:

complete-skill/
├── SKILL.md
├── references/
│   └── detailed-guide.md
├── examples/
│   └── sample-output.txt
└── scripts/
    └── helper.sh

3. frontmatter-templates.md

Copy-paste frontmatter examples for common patterns:

• Basic skill
• Skill with allowed-tools
• Multi-trigger skill

Acceptance Criteria

• examples/ directory exists in skill-development
• At least minimal-skill/SKILL.md with valid, copy-able template
• SKILL.md "Additional Resources" section references the examples
• Examples follow all documented best practices (third-person description, imperative body, etc.)

[sjnims]

PR submitted: #43