Rust builds work on Windows for large dependency graphs

Windows no longer fails with “filename or extension is too long” when compiling Rust crates with many dependencies. The full rustc argument list is routed through a response file, feature cfg values are preserved, and build-script crates use a native PowerShell wrapper instead of a Unix shell wrapper. Host tool lookup also skips extensionless mise shims, and failed graph actions now print response-file context to help diagnose toolchain issues.