feat(compress): move local dictionary sizing leaf to Rust

ZSTD_sizeof_localDict only combines the optional local dictionary buffer
size with the already-owned C dictionary size. Keep dictionary ownership and
workspace sizing in C, but pass the three scalar inputs to Rust so the leaf
uses explicit C size_t wrapping semantics. The CCtx NULL sizing guard and
surrounding ownership and call structure remain unchanged.

Test Plan:
- `cargo clippy --manifest-path rust/Cargo.toml --no-default-features --features compression` (before and after formatting) -- passed
- The same clippy command with `--benches` and `--tests` (before and after formatting) -- passed
- `cargo +nightly fmt --manifest-path rust/Cargo.toml` -- passed
- `cargo test --manifest-path rust/Cargo.toml --no-default-features --features compression` -- 272 passed
- `make -B -C lib -j2 lib` -- passed
- `make -C tests test-rust-lib-smoke` and direct `rustLibSmoke` execution -- passed
- `make -C tests -j2 fuzzer` -- passed
- `./fuzzer -s4560 -t56 -i57 -v` -- passed
- `git diff --check` and `git diff --cached --check` -- passed

lib/compress/zstd_compress.c

@@ -88,6 +88,8 @@ size_t ZSTD_rust_nextInputSizeHint(int inBufferMode,
                                    size_t inBuffPos);
 size_t ZSTD_rust_CStreamInSize(void);
 size_t ZSTD_rust_CStreamOutSize(void);
+size_t ZSTD_rust_sizeofLocalDict(int dictBufferPresent, size_t dictSize,
+                                 size_t cdictSize);
 
 /* Context-free compression-parameter selection and sizing leaves live in
  * Rust (rust/src/zstd_compress_params.rs).  This file retains
@@ -528,9 +530,9 @@ static void ZSTD_clearAllDicts(ZSTD_CCtx* cctx)
 
 static size_t ZSTD_sizeof_localDict(ZSTD_localDict dict)
 {
-    size_t const bufferSize = dict.dictBuffer != NULL ? dict.dictSize : 0;
     size_t const cdictSize = ZSTD_sizeof_CDict(dict.cdict);
-    return bufferSize + cdictSize;
+    return ZSTD_rust_sizeofLocalDict(dict.dictBuffer != NULL, dict.dictSize,
+                                     cdictSize);
 }
 
 static void ZSTD_freeCCtxContent(ZSTD_CCtx* cctx)