refactor: improve type safety and API clarity

[messense]

• source_distribution/unpack.rs: Replace bare (TempDir, PathBuf, PathBuf) tuple with named UnpackedSdist struct for self-documenting fields
• target/mod.rs: Change get_supported_architectures() to return &'static [Arch] instead of allocating Vec on every call

[Copilot]

Pull request overview

Refactors sdist unpacking to use a named return type for clearer APIs and updates architecture support lookup to avoid per-call allocations.

Changes:

• Introduces UnpackedSdist to replace the (TempDir, PathBuf, PathBuf) tuple return from unpack_sdist().
• Updates call sites (tests + build flow) to destructure UnpackedSdist.
• Updates get_supported_architectures() to return &'static [Arch] instead of allocating Vec<Arch> each call.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
tests/run/sdist.rs	Updates tests to destructure the new UnpackedSdist return type.
tests/common/other.rs	Updates shared test helper to destructure UnpackedSdist.
src/target/mod.rs	Returns static slices for supported architectures (no allocations).
src/source_distribution/unpack.rs	Adds UnpackedSdist struct and returns it from unpack_sdist().
src/source_distribution/mod.rs	Re-exports UnpackedSdist from the module.
src/metadata.rs	Replaces vec![]/Default::default() with explicit constructors (no semantic change).
src/main.rs	Adapts wheel-from-sdist build flow to new unpack API; renames local struct.
src/lib.rs	Re-exports UnpackedSdist from the crate root API.