Function build_plan_from_system 

pub fn build_plan_from_system(
    manifest: &Manifest,
    rocm_channel: &str,
    include_experimental: bool,
) -> Result<Vec<PlannerItem>, PlannerError>

Build a selection plan with automatic system detection.

This is the highest-level entry point that combines:

1. Hardware detection
2. Component detection
3. Version querying
4. Plan construction

Returns the plan items ready for display to the user.