addit-harness v0.1.3

Patch release: /addit-harness:setup now cleans up pre-plugin installs.

If you ran install.sh --target claude before the plugin existed, agents
and skills were copied unprefixed into ~/.claude/agents and
~/.claude/skills. The plugin now exposes the same content as
addit-harness:<name>, so those legacy copies show up as stale duplicates
alongside the prefixed versions.

/addit-harness:setup --scope global now detects and retires them. It
matches by line-level similarity rather than exact byte content (a legacy
install predates the plugin, so its content has usually drifted) or name
alone (which risks deleting an unrelated file that happens to share a
name). Anything retired is backed up first, same as everything else this
skill touches.