v0.3.1 — Fix plugin skill auto-discovery

Fix

• Add "skills": "./skills/" to .claude-plugin/plugin.json so /game-art:* slash commands are auto-registered when the plugin is installed
• Previously skills existed in skills/ but Claude Code couldn't discover them without the skills field in plugin.json

Other

• Bump version to 0.3.1
• Update asset registry with flat-roof house asset

Full Changelog: v0.3.0...v0.3.1