This commit adds support for installing Claude Code plugins via a new `plugins` input parameter.
Changes:
- Added `plugins` input to action.yml (comma-separated list)
- Created `install-plugins.ts` with plugin installation logic
- Added comprehensive tests in `install-plugins.test.ts`
- Updated base-action index.ts to call plugin installation
- Plugins are installed after settings setup but before Claude execution
Usage example:
```yaml
- uses: anthropic-ai/claude-code-action@main
with:
plugins: "feature-dev,test-coverage-reviewer"
```
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
