Rust Ecosystem

Part of src/cmds/ — see also docs/contributing/TECHNICAL.md

Specifics

• cargo_cmd.rs uses restore_double_dash() fix: Clap strips -- but cargo needs it for test flags (e.g., cargo test -- --nocapture)
• runner.rs is a generic two-mode runner (err = stderr only, test = failures only) used as fallback for commands without a dedicated filter
• runner.rs is also referenced by other modules outside this directory as a generic command executor