Brummel
215f403496
Iteration-1 plan for #175: replace the hand-rolled aura-cli argv parser with a clap derive parser (scoped `aura <sub> --help`, `--version`/`-V`, per-flag Options section, `--flag=value`/`--`/long-opt abbreviation), behaviour-preserving on exit codes. Task 1 adds clap + RED tests for the new behaviour; Task 2 is the atomic migration + renegotiation of the help/usage pins the migration inverts (the four dual-grammar subcommands mapped as optional [blueprint] positional + post-parse is_file() dispatch; execution layer untouched). The exit-code split is iteration 2. refs #175