chore: restore Rust quality baseline

[kholdrex]

Summary

Restores the Rust formatting and Clippy quality baseline so routine quality gates pass again. The change applies rustfmt consistently across source, examples, and tests, then fixes or explicitly scopes existing Clippy findings that were blocking -D warnings.

Changes

• Applied cargo fmt across the crate, examples, and tests.
• Addressed mechanical Clippy findings such as redundant field names, manual range checks, clone mapping, Into implementations, and missing Default implementations.
• Added explicit lint allowances where existing example/test complexity is outside this baseline cleanup scope.

Test Plan

• cargo fmt --all -- --check
• cargo clippy --all-targets --all-features -- -D warnings
• cargo test --all-features