Include the scanner version in Markdown reports

[guvenemre]

Markdown reports currently show the target, model, profile, score, and generation time, but omit the CompatCanary version that produced the result. Including the scanner version makes copied reports easier to reproduce and compare after releases.

Proposed behavior

Add a line near the top of Markdown output using the existing report metadata, for example:

- **Scanner:** `compatcanary 0.2.2`

Acceptance criteria

• renderMarkdown(report) displays report.scanner.name and report.scanner.version.
• The value comes from the report object; do not import or duplicate the package version in the Markdown renderer.
• JSON and text report behavior remains unchanged.
• A focused test proves the Markdown report contains the scanner name and version.
• README or schema documentation is updated only if needed to keep the documented Markdown example accurate.
• npm run check, npm test, and npm run evidence:check pass.

Likely files

src/reporters.js and test/integration.test.js or a new focused reporter test.

This task uses the existing mock report data and requires no provider account or API key. If you would like to work on it, leave a comment before opening a focused pull request.