feat: support source.filter for URL and archive path sources

[wolfv]

Summary

This PR extends the source.filter field to support url sources and path sources that point to archives. Previously, filtering was only available for git sources. The filter is now applied to the contents of extracted archives, allowing large source tarballs to be trimmed down to only the parts needed for the build.

Key Changes

• Recipe Schema Updates: Added filter field to UrlSource in both stage0 and stage1 recipe structures with proper serialization handling
• Parser Enhancement: Extended the URL source parser to recognize and parse the filter field alongside existing fields like url, sha256, and patches
• Source Extraction Logic: Modified copy_from_cache() to accept and apply glob filters when copying extracted archive contents to the destination directory
• Path Source Archives: When a path source points to an archive file, it's now converted to a temporary URL source with the filter applied during extraction
• Variable Evaluation: Added filter evaluation in the stage0 evaluation logic to support variable interpolation within glob patterns
• Documentation: Added comprehensive examples in recipe_file.md showing both simple list-based and include/exclude mapping-based filter syntax for URL sources
• Tests: Added unit tests for parsing URL sources with filters and an end-to-end test with a real archive demonstrating filter functionality

Implementation Details

• The filter is applied at the extraction stage using the existing copy_dir::CopyDir builder with the new with_globvec() method
• Filters support both simple list syntax (["cmake/*", "clang/*"]) and structured include/exclude mappings
• The implementation reuses the existing IncludeExclude and GlobVec types already used for git source filtering
• Snapshot tests were updated to reflect the new filter: [] field in serialized output

https://claude.ai/code/session_01RxSDwdYTY8h7T8VRHR5wmD

[wolfv]

I also submitted a CEP update: conda/ceps#176

[wolfv]

Thanks for the pointer to conda/ceps#176. Since CEP-0014 specifies filter on url, path, and git sources, I've pushed a follow-up commit (41f28d5) adding git source support too — the filter is applied to the checked-out tree, mirroring the url/path behavior. Parser tests and an end-to-end check against a local git repo confirm it works. The PR now covers all three source types from the CEP.

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[h-vetinari]

Super nice! 🤩