[Good first issue]: Verify the no-clone demo on Windows

[thangldw]

User outcome

A Windows user can run the credential-free demo without cloning the repository and receives the same blocked candidate plus HTML evidence.

Scope

• Exercise uvx ragops demo on a supported Windows GitHub Actions runner.
• Assert the candidate decision is BLOCK and the standalone HTML report exists.
• Add concise PowerShell guidance only where it differs from the canonical command.
• Keep the existing Linux/macOS path unchanged.

Acceptance criteria

• The smoke path needs no account, model API key, or repository checkout.
• It verifies the expected exit behavior and generated files.
• Documentation does not add a second competing quickstart.
• ruff check . and PYTEST_DISABLE_PLUGIN_AUTOLOAD=1 pytest -q pass.

Non-goals

Do not add a Windows-only runtime dependency or publish a new package version.