feat(compress): move frame-block preparation order into Rust

Move the frame-chunk match-state preparation policy into Rust while keeping
window and workspace mutations behind narrow C callbacks. Rust now guarantees
the original overflow-correction, dictionary-validity, maximum-distance, and
nextToUpdate-clamp order; the C side retains the private ZSTD_MatchState_t
layout and exact primitive operations.

Test Plan:
- cargo fmt --manifest-path rust/Cargo.toml -- --check
- ulimit -v 41943040 && CARGO_BUILD_JOBS=1 cargo test --manifest-path rust/Cargo.toml frame_chunk --lib (3 passed)
- ulimit -v 41943040 && CARGO_BUILD_JOBS=1 cargo test --manifest-path rust/Cargo.toml --lib (691 passed)
- ulimit -v 41943040 && CARGO_BUILD_JOBS=1 cargo clippy --manifest-path rust/Cargo.toml --all-targets -- -D warnings
- ulimit -v 41943040 && MAKEFLAGS=-j1 make -B -C programs -j1 zstd
- ulimit -v 41943040 && MAKEFLAGS=-j1 make -C tests -j1 test-zstream ZSTREAM_TESTTIME=-T1s (84 tests and both short fuzz rounds passed)

rust/README.md

@@ -97,7 +97,8 @@ zstd ABI:
     job-creation decisions, compression-job stage sequencing and error flow,
     pending-output decisions through scalar job projections, and frame
     progression's job-ring scan, error normalization, and active-worker
-    accounting.
+    accounting.  Rust also owns frame-block preparation ordering; C callbacks
+    retain the private match-state window and workspace operations.
 - Dictionary support
   - `zstd_ddict` owns, loads, copies, and references decode dictionaries.
 - Legacy decoding
@@ -148,7 +149,7 @@ shared- and separate-destination decompression scheduling,
 single-threaded stream initialization and the buffered/stable stream state
 machine, MT stream initialization, MT outer scheduling and flush policy, MT
 compression-job stage sequencing and error flow, MT frame-progression job
-aggregation, public sequence-API
+aggregation, frame-block preparation ordering, public sequence-API
 orchestration, sequence-store and block policy, external-producer invocation
 and success-path validation, external-sequence-store reset,
 external-sequence/literals block loop, optional-format decompression loops,