Improve Vite plugin build strategy

[petermasking]

Currently, the Vite plugin can only run after the Jitar build process because it relies on its output to bundle the segment-aware modules. While this works, it has two drawbacks:

1. The plugin has knowledge of Jitar's segmentation strategy and depends on its output structure (which hurts maintainability).
2. The build order is forced: Jitar must run before Vite (which hurts flexibility).

To address these issues, we need to rethink the plugin design.