Run `cargo fmt` across all Rust source files to enforce consistent
formatting (import ordering, line wrapping, match arm braces).
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Standardize code formatting across all 173 Rust source files
using rustfmt. No functional changes - purely cosmetic.
This establishes a consistent code style baseline for the
project going forward.