Move skills/zio-harness into plugins/zio-harness/ as a self-contained
plugin with its own .claude-plugin/plugin.json. Add a second marketplace
entry (zio-harness@1.0.0) and bump the harness plugin to 1.3.0 since it no
longer bundles zio-harness. Single ownership: harness ships only the
harness skill, zio-harness ships only the zio-harness skill.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
