ddidderr
4304c0af40
Legacy detection, frame-size queries, one-shot decode, and buffered streaming were still routed through the C header dispatcher even though every historical v0.1 through v0.7 decoder is already ported under Rust feature gates. The C implementation also duplicated the support-level boundary independently from the Rust archive selection. Move the dispatcher and stream lifecycle to Rust using the existing DCtx field projection. Rust now selects the version, preserves the null-buffer and position semantics, initializes and frees buffered legacy contexts, and calls the frozen per-version modules. C retains only the configuration leaf that reports ZSTD_LEGACY_SUPPORT plus the private DCtx layout and trace helpers, so library, program, and test builds can still choose different support levels. Test Plan: - `cargo test --manifest-path rust/Cargo.toml --no-default-features --features compression,decompression,dict-builder,legacy-v01,legacy-v02,legacy-v03,legacy-v04,legacy-v05,legacy-v06,legacy-v07 --all-targets -- --test-threads=1` -- 528 passed. - Native `test-legacy`, `test-invalidDictionaries`, `test-decodecorpus`, and `test-zstd` -- passed. - Strict C syntax checks with legacy support 0, 4, 5, and 7 -- passed. - `cargo clippy` default, benches, and tests for library and CLI -- passed.