docs: document mutiny init/run/test CLI flags from --help

[CodewithJha]

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Context

README Commands is a high-level table. Full flags are discoverable via --help, but newcomers often want them written down once.

Goal

Document the real mutiny init / run / test flags (from --help) in README and/or a small docs/CLI.md.

Why it matters

Reduces “what does --no-hosted do?” friction and keeps install messaging honest (from source via uv, not PyPI yet).

Acceptance criteria

• List real flags from uv run mutiny {init,run,test} --help (at least --path, --force, --no-hosted, --hosted-url, --failed, --json, --no-report if present)
• Keep install path honest (from source / uv sync; no false PyPI claim)
• Prefer expanding README Commands or add docs/CLI.md + link from docs/README.md / README
• PR description links this issue

Suggested files

• README.md (Commands section)
• Optional: docs/CLI.md, docs/README.md

Out of scope

• Changing CLI behavior, adding flags, or claiming PyPI publish

Hints

• Run each --help and copy names/defaults verbatim — do not invent flags.
• One short “when to use --no-hosted” sentence helps more than a long prose page.
• Current Commands table already names a few flags; expand rather than duplicate the Quick start.

Difficulty

S · docs / DX · no code required

Docs

• Catalog: GOOD_FIRST_ISSUES.md #2
• README Commands