Rust CLI taste

# Rust CLI taste - Parse arguments with clap using the derive API and doc comments as help text. Confidence: 0.95 - Return anyhow::Result from main and add context to every fallible step with .context(). Confidence: 0.90 - Define library error types with thiserror and keep anyhow in the binary only. Confidence: 0.85 - Split the crate into a thin main.rs and a lib.rs that holds the real logic for testing. Confidence: 0.85 - Write normal output to stdout and logs, progress and errors to stderr. Confidence: 0.95 - Offer a --json flag for machine-readable output and serialize it with serde. Confidence: 0.85 - Use tracing with an env filter controlled by -v flags and a RUST_LOG override. Confidence: 0.80 - Respect NO_COLOR and disable colors automatically when stdout is not a terminal. Confidence: 0.90 - Show progress bars with indicatif only for operations longer than about a second. Confidence: 0.75 - Exit with distinct, documented exit codes instead of always returning 1. Confidence: 0.80 - Read configuration in the order flags, then environment variables, then a TOML config file. Confidence: 0.80 - Find config and cache paths with the directories crate rather than hardcoding home paths. Confidence: 0.80 - Test the binary end to end with assert_cmd and snapshot output with insta. Confidence: 0.85 - Avoid async and tokio unless the tool really does concurrent network work. Confidence: 0.75 - Generate shell completions and a man page with clap_complete and clap_mangen at build time. Confidence: 0.75 - Ship prebuilt binaries for Linux, macOS and Windows with cargo-dist from GitHub Actions. Confidence: 0.80 - Run cargo clippy with warnings denied and cargo fmt --check in CI. Confidence: 0.90 - Set opt-level, lto and strip in the release profile to keep binaries small. Confidence: 0.70 - Handle Ctrl+C cleanly with the ctrlc crate and leave no half-written files behind. Confidence: 0.80