Move the residual ZSTD_resetCCtx_internal sequencing into a Rust policy
entrypoint. The Rust side now owns the plan-to-workspace-to-tail order and
scalar hand-off, while C retains private workspace checks, context
initialization, match-state reset, and pointer publication callbacks. Preserve
error short-circuiting and the existing static, dynamic, LDM, and index-reset
behavior.
Test Plan:
- cargo fmt --manifest-path rust/Cargo.toml --all -- --check
- git diff --check
- Full capped Rust, native, CLI, and upstream test suites to follow