Split the single cli_tests trycmd function into 14 per-subcommand test
functions so nextest can parallelize them. Delete header.toml and
verbose.toml doctor fixtures that ran live network probes — the existing
dry-run-flag.toml and help.trycmd already cover the same output assertion.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>