Keep the C-owned trace slot behind an explicit pointer projection so the
Rust trace boundary owns the complete enabled-call lifecycle. Rust now reads
the context, publishes the record, and clears the slot after the callback;
C only supplies private CCtx fields and the weak callback adapter.
Test Plan:
- ulimit -v 41943040; CARGO_BUILD_JOBS=1 cargo check --tests (rust)
- ulimit -v 41943040; CARGO_BUILD_JOBS=1 cargo clippy --tests -- -A clippy::manual-bits -D warnings (rust)
- ulimit -v 41943040; make -j1
- ulimit -v 41943040; make -j1 -C tests test
- Focused trace lifecycle test added; standalone cargo test remains link-blocked by the existing C-owned decompression view symbols.
ddidderr
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