Plugin version management: install specific version, uninstall by version

Problem

The plugin system caches plugins by version (~/.claude/plugins/cache/{marketplace}/{plugin}/{version}/), but there's no way for users to:

1. Install a specific version of a plugin (/plugin install name@1.0.0)
2. Uninstall a specific cached version (/plugin uninstall name --version 1.0.0)
3. List cached versions of a plugin
4. Rollback to a previous version

When a plugin bumps its version, the old cache remains on disk with no way to clean it up other than manually deleting folders. Users who want to pin to a stable version or test a new version before committing have no tooling for this.

Proposed solution

Install with version

/plugin install name@marketplace --version 1.0.0
/plugin install name@marketplace --ref v1.0.0

List cached versions

/plugin versions name
# Output:
# name@marketplace
#   1.0.0 (installed 2026-03-10)
#   1.1.0 (installed 2026-03-11, active)

Uninstall specific version

/plugin uninstall name --version 1.0.0
# Removes ~/.claude/plugins/cache/{marketplace}/{plugin}/1.0.0/

Rollback

/plugin use name --version 1.0.0
# Switches active version without reinstalling

Context

Discovered this while maintaining an internal plugin at Nubank that needed a version bump from 1.0.0 to 1.1.0. After the bump, users had both versions cached with no way to clean up the old one from the CLI.