refactor(compress): expose pure parameter policy leaves from Rust

The compression-parameter check, clamp, and cycle-log helpers were still
translation-unit C bodies that only forwarded value arguments to Rust. That
left redundant C ownership and made the direct Rust ABI names differ from the
public or internal C symbols used by callers. Export the existing C names from
the Rust parameter module and remove the forwarding bodies. Crate-local aliases
retain the old Rust-side names for existing Rust callers; all private context,
configuration, assertion, and stateful adapters remain on the C side.

Test Plan:
- `cc -fsyntax-only -Ilib -Icommon lib/compress/zstd_compress.c` -- passed.
- `cargo +nightly fmt --manifest-path rust/Cargo.toml --all -- --check` -- passed.
- `git diff --check` and `git diff --cached --check` -- passed.
- Heavy cargo, make, and test commands were intentionally not run per scope.

rust/src/zstd_compress_params.rs

@@ -1136,7 +1136,7 @@ pub extern "C" fn ZSTD_defaultCLevel() -> c_int {
 }
 
 /* Keep existing Rust parameter-module callers source-compatible while the
- * public C symbols are owned directly by these Rust leaves. */
+ * C symbols are owned directly by these Rust leaves. */
 pub(crate) use ZSTD_defaultCLevel as ZSTD_rust_params_defaultCLevel;
 
 /// Returns bounds for the seven core compression parameters and compression
@@ -1148,7 +1148,7 @@ pub extern "C" fn ZSTD_rust_params_getBounds(param: c_int) -> ZSTD_bounds {
 
 /// Checks the seven fields of `ZSTD_compressionParameters`.
 #[no_mangle]
-pub extern "C" fn ZSTD_rust_params_checkCParams(cparams: ZSTD_compressionParameters) -> usize {
+pub extern "C" fn ZSTD_checkCParams(cparams: ZSTD_compressionParameters) -> usize {
     check_cparams(cparams)
 }
 
@@ -1166,7 +1166,7 @@ pub extern "C" fn ZSTD_rust_params_assertEqualCParams(
 
 /// Clamps the seven fields of `ZSTD_compressionParameters` to public bounds.
 #[no_mangle]
-pub extern "C" fn ZSTD_rust_params_clampCParams(
+pub extern "C" fn ZSTD_clampCParams(
     cparams: ZSTD_compressionParameters,
 ) -> ZSTD_compressionParameters {
     clamp_cparams(cparams)
@@ -1174,10 +1174,16 @@ pub extern "C" fn ZSTD_rust_params_clampCParams(
 
 /// C ABI for `ZSTD_cycleLog()`.
 #[no_mangle]
-pub extern "C" fn ZSTD_rust_params_cycleLog(hashLog: u32, strategy: c_int) -> u32 {
+pub extern "C" fn ZSTD_cycleLog(hashLog: u32, strategy: c_int) -> u32 {
     cycle_log(hashLog, strategy)
 }
 
+/* Keep existing Rust parameter-module callers source-compatible while the
+ * C symbols are owned directly by these Rust leaves. */
+pub(crate) use ZSTD_checkCParams as ZSTD_rust_params_checkCParams;
+pub(crate) use ZSTD_clampCParams as ZSTD_rust_params_clampCParams;
+pub(crate) use ZSTD_cycleLog as ZSTD_rust_params_cycleLog;
+
 /// C ABI for private `ZSTD_getCParamRowSize()`.
 #[no_mangle]
 pub extern "C" fn ZSTD_rust_params_getCParamRowSize(