Fully support `strict` on plugin entries in the marketplace

### Describe the feature or problem you'd like to solve

strict is in the schema for a plugin entry in the marketplace listing, but it is not respected. The default is true and that's what the CLI currently supports, but we should support when a marketplace's plugin entry has this set to false

### Proposed solution

Add support for strict: false and plumb that through to the various plugin acquisition methods. This would allow the marketplace to control the parts of the plugin that are included rather than the (potentially remote) plugin source's plugin.json.

### Example prompts or workflows

_No response_

### Additional context

https://code.claude.com/docs/en/plugin-marketplaces#strict-mode