Rust Native Linking

Hand these topics to sibling skills, when they are installed:

• The rust-unsafe skill owns FFI soundness, layout, ownership, and safety contracts.
• The cargo-workflows skill owns workspace layout, profiles, features, and general cross-target orchestration.
• The rust-android-build skill owns NDK selection, Android ABI policy, page size, jniLibs, APK or AAB checks, and the Android export gate.
• The rust-wasm skill owns WebAssembly link errors, including undefined symbol on wasm32 targets.

Do not add a native build step when an existing Rust crate already owns the same library. Reuse its *-sys crate and its links contract.