Move ZSTD_CCtx_reset directive handling into a Rust-owned state machine while keeping dictionary cleanup and parameter reset behind C callbacks. Preserve the original session ordering, stage error boundary, completion/max-block flag updates, and reset error propagation across the ABI bridge.
Test Plan:
- cargo test --manifest-path rust/Cargo.toml --lib
- cargo clippy --manifest-path rust/Cargo.toml --all-targets -- -D warnings
- make -B -C programs -j1 zstd
- focused reset_cctx unit tests