Fix alias resolution for @rubygems/* paths

[Copilot]

Aliases pointing to @rubygems/* paths were left unresolved, breaking imports like:

config.proscenium.aliases = {
  'lexxy-variables' => '@rubygems/lexxy/app/assets/stylesheets/lexxy-variables.css'
}

Changes

@rubygems/ handler*: Re-resolve gem metadata when an aliased path is also a @rubygems/* path. Previously, gem name and path from the original import were used even after alias substitution.

General handler: Delegate to @rubygems/* handler via build.Resolve() when a bare module alias targets a @rubygems/* path. This ensures proper processing through the rubygems resolution pipeline including CSS-from-JS detection.

Both scenarios now correctly resolve the target path through the full resolution chain.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Alias to a @rubygems/* path is not resolved</issue_title>
<issue_description>When an alias is defined that points to a @rubygems/* path, the resulting path is not resolved. It seems to be left as is.

{
'lexxy-variables.css' => '@rubygems/lexxy/app/assets/stylesheets/lexxy-variables.css'
}

The above will resolve lexxy-variables.css to @rubygems/lexxy/app/assets/stylesheets/lexxy-variables.css.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Alias to a @rubygems/* path is not resolved #57

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