feat: make shell compatibility checks one-click

[Mresyzz]

Problem

The repository gets views but has no repeatable downstream install path. New users still need to assemble a workflow by hand.

What changed

• Add a zero-configuration starter workflow for shell-file changes.
• Upload a Markdown compatibility report as a workflow artifact.
• Add citation metadata and installer/bootstrap keywords for discoverability.
• Mark the project Beta and correct the roadmap's delivered v0.5/v0.6 entries.
• Update the README with a direct copy path and no-account/no-signup explanation.
• Prepare v0.6.1 so the PyPI metadata changes are actually published.

Validation

• python -m pytest -q -m "not integration" — 103 passed, 1 skipped
• python -m twine check dist/opsscript_gate-0.6.1* — passed
• git diff --check — passed
• Docker integration tests were skipped because no Docker daemon is available locally.

Merging this PR triggers the existing release workflow to publish v0.6.1, so the version bump is intentional.