Keep the compression context extraction and the weak trace hook adapter in C,
where the private CCtx layout and platform-specific tracing declarations remain
available. Project only the scalar trace inputs and callback through an explicit
ABI-checked boundary so Rust owns the enabled check, stable record layout,
version field, compression-only null fields, and end-of-trace policy. The C
entry point still clears traceCtx after Rust returns, preserving the old
single-use lifecycle and keeping trace-disabled builds free of weak-hook calls.
Test Plan:
- ulimit -v 41943040; CARGO_BUILD_JOBS=1 cargo check --manifest-path rust/Cargo.toml --tests
- ulimit -v 41943040; CARGO_BUILD_JOBS=1 cargo clippy --manifest-path rust/cli/Cargo.toml --all-targets -- -D warnings
- ulimit -v 41943040; CARGO_BUILD_JOBS=1 make -j1
- ulimit -v 41943040; make -j1 -C tests test