ZSTD_freeCCtx previously passed one C callback that bundled dictionary,
multithreaded context, workspace, and heap-object teardown. That left the
lifetime order inside private C control flow and made the public destruction
policy harder to audit. Project the four private operations separately and
let Rust enforce the original dictionary, MT-context, workspace, and
object order while preserving the static-context and workspace-embedded
object guards. The callbacks still own the C layouts and custom allocator
operations.
Test Plan:
- `ulimit -v 41943040; cargo +nightly fmt --manifest-path rust/Cargo.toml --all -- --check` -- passed
- `ulimit -v 41943040; CARGO_BUILD_JOBS=1 cargo clippy --manifest-path rust/Cargo.toml --all-targets -- -D warnings` -- passed
- Broader native and original-test verification remains pending for the complete batch.