Make Rust the owner of the compression-job preparation sequence: publish the descriptor, reset the reusable input state, and publish terminal frame state last. Keep all MT job and stream layouts in C behind three focused callbacks, and preserve the nonterminal and terminal branches exactly.
Test Plan: ulimit -v 41943040; CARGO_BUILD_JOBS=1 cargo clippy --manifest-path rust/Cargo.toml --all-targets -- -D warnings; cargo +nightly fmt --manifest-path rust/Cargo.toml --all -- --check; GCC and Clang syntax-only checks; make -j1 -C tests test (all 41 shell tests, fuzzer, zstd tester, and zstream tester passed).