Move fileio preference and context allocation, defaults, setters, and small
query helpers into Rust while keeping the actual file operations in C. Keep
the C structs and ABI declarations as anchors, and make the CLI build track
the new Rust source.
Test Plan:
- rustfmt +nightly --check --edition 2021 rust/src/fileio_prefs.rs rust/cli/src/lib.rs
- RUSTC_WRAPPER= CARGO_BUILD_RUSTC_WRAPPER= cargo test --manifest-path rust/cli/Cargo.toml
- RUSTC_WRAPPER= CARGO_BUILD_RUSTC_WRAPPER= cargo clippy --manifest-path rust/cli/Cargo.toml --all-targets -- -D warnings
- git diff --cached --check
ddidderr
60877175a4