feat(cli): move benchmark bridge into Rust

Move benchmark parameter normalization and dispatch into the Rust CLI archive while retaining the stable C launcher entry point. Keep compact CLI variants benchmark-free and add an explicit helpers feature for the C test generators.

Test Plan:

- cargo test --manifest-path rust/cli/Cargo.toml --no-default-features --features benchmark

- cargo test --manifest-path rust/cli/Cargo.toml --no-default-features --features helpers

- cargo clippy --manifest-path rust/cli/Cargo.toml --all-targets --no-default-features --features cli,compression,decompression,benchmark

- cargo clippy --manifest-path rust/cli/Cargo.toml --all-targets --no-default-features --features helpers

- make -B -C programs -j2 zstd zstd-small zstd-frugal

- make -B -C tests -j2 test-cli-tests

- programs/zstd -b1i1 -q

rust/cli/Cargo.toml

@@ -7,13 +7,18 @@ edition = "2021"
 crate-type = ["staticlib"]
 
 [features]
-default = ["cli", "compression", "decompression"]
+default = ["cli", "compression", "decompression", "benchmark"]
 # The command-line parser and dispatch layer, which requires the C fileio
 # backend at link time. Program archives enable it; C test binaries link a
 # helpers-only archive (timefn) built without it.
 cli = []
 compression = []
 decompression = []
+helpers = []
+# The integrated benchmark archive is optional so zstd-small and zstd-frugal
+# can omit every benchmark implementation and its timing/data-generator
+# dependencies.
+benchmark = ["compression"]
 
 [dependencies]
 libc = "0.2"