Brummel
5c6de45b6e
Two CLI-UX defects the Stage-1 R fieldtest surfaced (#131): 1. Tap discovery. `aura chart <name> --tap <bad>` rejected an unknown tap but the error omitted the valid names. filter_to_tap now enumerates the run's available taps in the message ("... (available: equity, exposure)"), so the user can correct a typo instead of guessing -- refuse, but help. 2. Uniform --help. `aura chart --help` errored with "unexpected chart argument '--help'" (exit 2) and `aura run --help` leaked usage to stderr via the error path, while bare `aura --help` printed to stdout (exit 0). main() now intercepts `--help`/`-h` anywhere in the invocation, prints usage to stdout, and exits 0 -- uniform for every subcommand. The now-dead bare-flag match arm is removed (the early intercept covers it). RED-first: the existing chart_tap_nonexistent test gains an available-taps assertion (was: message had no names), and a new per_subcommand_help test pins `aura <sub> --help` -> stdout usage + exit 0 for run/chart/sweep/walkforward/ mc/graph/runs (was: chart --help exited 2). Unknown-subcommand stays exit 2. Verified: clippy --all-targets -D warnings clean; full suite 514 passed / 0 failed (one new test); live `aura chart --help` prints usage to stdout, exit 0. closes #131