Support anonymous GitHub contributors and human hyphenated author names

[beanbean9339]

Problem

GitHub's contributors endpoint can include anonymous human commit authors, and human hyphenated names can be mistaken for handles or lose punctuation when normalized.

Scope

Request anonymous contributors, retain type Anonymous while filtering bots, preserve human Title-Case hyphenated names in GitHub-sourced author inputs, and avoid changing normalization for other metadata sources. Independent of the #56 fallback-count fix.

Acceptance criteria

• Anonymous human contributor names may become authors; bots remain excluded.
• Human hyphenated names remain intact; username-like values remain excluded.
• Regression tests cover both behavior and unchanged non-GitHub normalization.