Skills and commands are now merged, so SKILL.md name fields surface
in the UI as slash commands. Upper Space names like 'Hook Development'
become '/Hook Development', which doesn't work since user-invoked
commands don't support spaces.
Rename all affected SKILL.md name fields to lower-kebab-case:
- hookify: Writing Hookify Rules -> writing-hookify-rules
- plugin-dev: Agent Development -> agent-development
- plugin-dev: Command Development -> command-development
- plugin-dev: Hook Development -> hook-development
- plugin-dev: MCP Integration -> mcp-integration
- plugin-dev: Plugin Settings -> plugin-settings
- plugin-dev: Plugin Structure -> plugin-structure
- plugin-dev: Skill Development -> skill-development
Also update references in plugin-dev/README.md.
