plugin-dev skill-development: document hyphenated naming requirement for skill names

Summary

The skill-development skill in the official plugin-dev plugin shows examples with space-separated title case names in YAML frontmatter (e.g., name: Skill Name), but slash command triggering requires hyphenated lowercase names (e.g., name: skill-name).

Problem

The guide's examples use:

name: Skill Name

But in practice, /skill-name only works when the frontmatter uses:

name: skill-name

Using name: Skill Name causes /skill-name to fail with "Unknown skill" because only the first word matches.

Suggested Fix

1. Update the SKILL.md frontmatter examples to use hyphenated lowercase names
2. Add a note in the "Metadata Quality" section explaining that the name field should use lowercase-hyphenated format since it's used as the slash command trigger (e.g., name: my-skill triggers via /my-skill)

Affected File

plugin-dev/skills/skill-development/SKILL.md — multiple example blocks showing name: in frontmatter