SwiftUsdShell binary package

This existing package publishes two deliberately separate surfaces:

• legacy SwiftUsdShell and SwiftUsdShellOpenUSD products for LTS consumers;
• SwiftUsdShellRuntime, the self-contained product-neutral runtime used by the OS 27 private engine libraries.

The 0.5.x runtime line is produced only by the remote M5 workflow in Reality2713/SwiftUsd-binaries. The package contains no engine source and owns no product capability. Engine repositories depend on a compatible 0.5.x runtime range; app roots pin the exact patch tested by the binary release lock.

A toolchain-only patch updates this package without retagging unchanged engines. Version-dependent runtime, plugins, and exact engine tags are still tested together before publication.