Keep the heapmode guard, stack-owned ZSTD_DCtx, static initialization, and
private context layout in C. Once the context is initialized, Rust now owns the
one-shot stack-context policy: it clears the projected static-size marker and
dispatches the existing ZSTD_decompressDCtx implementation through the opaque
context pointer.
Add matching C/Rust view-layout assertions and focused callback tests covering
static-size clearing, argument forwarding, and null-context rejection.
Test Plan:
- `ulimit -v 41943040; cargo +nightly fmt --manifest-path rust/Cargo.toml --all -- --check`
- `ulimit -v 41943040; CARGO_BUILD_JOBS=1 cargo clippy --manifest-path rust/Cargo.toml --all-targets -- -D warnings`
- `ulimit -v 41943040; make -j1`
- `ulimit -v 41943040; make -j1 -C tests test` (all upstream tests completed successfully)
- Standalone Rust unit linking remains unavailable without the C-owned bridge symbols; the integrated build and upstream C/Rust oracle supplied the runtime/link coverage.
ddidderr
870d6a2e40