Move the MT LDM overlap predicate behind the original
ZSTDMT_doesOverlapWindow() by-value ABI. Rust now owns the half-open range
calculation through a checked representation of Buffer and ZSTD_window_t;
C retains the synchronization and context orchestration around the callback.
Test Plan:
- `cc -fsyntax-only -Ilib -Ilib/common -Ilib/compress -Ilib/decompress -Ilib/dict -Ilib/legacy lib/compress/zstdmt_compress.c` -- passed.
- `cargo +nightly fmt --manifest-path rust/Cargo.toml --all -- --check` -- passed.
- `git diff --check` and `git diff --cached --check` -- passed.
- Heavy verification intentionally deferred until the combined seam set is ready.
ddidderr
8919e0d292