fix: only shim bin wheels during auditwheel repair

[messense]

Summary

• only enable the bin-wheel shim layout when auditwheel=repair will bundle external libraries
• keep auditwheel=warn, check, skip, no-library, and WASI builds on the normal .data/scripts/ layout
• add a focused unit test for the shim decision matrix

Rationale

Maturin 1.13.2 started moving bin artifacts into {dist}.scripts/ whenever external libraries were detected. On macOS and Windows, the default auditwheel mode is warn, which reports external libraries but does not graft them into the wheel. That produced shim-only wheel layouts without bundled .dylibs/.libs, which changed wheel contents unexpectedly for consumers such as astral-sh/uv#19468.

The shim is only needed when repair mode copies libraries into platlib and the binary needs a predictable relative path to those bundled libraries.

Checks

• cargo fmt --all
• cargo test --lib build_orchestrator::tests::test_should_use_bin_shim_only_for_repair_with_external_libs -- --nocapture
• cargo test --lib
• cargo clippy --tests --all-features -- -D warnings
• git diff --check
• pre-commit commit hooks (cargo fmt, cargo deny, general hooks)

[Copilot]

Pull request overview

This pull request refines when maturin uses the “bin wheel shim” layout for binary wheels so that wheel contents only change when auditwheel=repair will actually bundle external libraries, avoiding unexpected layout changes in warn/check/skip modes (notably on macOS/Windows where default is warn).

Changes:

• Gate bin-wheel shim layout behind a new should_use_bin_shim(...) helper that requires AuditWheelMode::Repair, non-WASI target, and detected external libraries.
• Keep non-repair auditwheel modes (and WASI) on the standard .data/scripts/ layout even if external libraries are detected.
• Add a focused unit test covering the shim decision matrix.

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