* line_index.rs: replace manual `x % BLOCK_SIZE == 0` with
`.is_multiple_of(BLOCK_SIZE)` (Rust 1.81+).
* line_index.rs: gate three pub(crate) accessor methods
(`sampled_offsets`, `total_lines`, `has_trailing_newline`) behind
`#[cfg(test)]`. They are only consumed by tests in file_reader.rs;
marking them test-only removes them from production builds entirely,
eliminating the dead_code warning without suppressing it.
* json.rs: drop redundant `Some(... .ok()?)` wrapper in
parse_json_object_with_duplicates. `.ok()` already returns Option,
so wrapping it in Some and unwrapping with ? was a no-op.
No behavior change. Unblocks `cargo clippy --workspace -- -D warnings`.
dailz
95f259a2bb