Keep C responsible for extracting the cdict and CCtx scalar fields while
moving the attach-versus-copy mode decision into the Rust parameter module.
The Rust ABI short-circuits absent cdicts and reuses the established
attachment predicate, preserving unknown-size, force-attach, force-copy, and
force-window behavior.
Test Plan:
- cargo test --manifest-path rust/Cargo.toml --no-default-features
--features compression
cparam_mode_preserves_cdict_presence_and_attachment_policy -- passed
- make -B -C lib -j2 lib -- passed
- make -C tests -j2 fuzzer -- passed
- ./tests/fuzzer -s4560 -t47 -i48 -v -- passed
- Required clippy normal/benches/tests, nightly fmt, and diff checks -- passed
ddidderr
3c51a97814