Apply clippy recommendations

[scaryrawr]

No description provided.

[Copilot]

Pull request overview

This PR applies a small set of Rust/Clippy-driven cleanups across the Rust CLI (apps/sl) and core rendering library (libraries/libsl) without changing intended runtime behavior.

Changes:

• Simplifies lifetime annotations in libsl helper code (car_text) using elided lifetimes.
• Rewrites equivalent boolean/match patterns into more idiomatic Rust (if x >= 0, if let Ok(...)).
• Removes an unused clap import while keeping the derive/attributes intact.

Show a summary per file

File	Description
libraries/libsl/src/print_car.rs	Removes unnecessary explicit lifetime parameters from car_text signature.
libraries/libsl/src/mvaddstr.rs	Replaces a negated comparison with an equivalent direct comparison for clarity.
apps/sl/src/main.rs	Replaces match-with-empty-Err arms with if let Ok(...) patterns in two loops.
apps/sl/src/cli.rs	Removes an unused clap::{command, ...} import while keeping #[command(...)] attribute usage.

Copilot's findings

• Files reviewed: 4/4 changed files
• Comments generated: 0