Improve font rendering

[PeteHaughie]

Summary

• Improve font rendering preserve alpha and make strokes outline-only
• Simple API font face loading
• System fonts are listed first but custom TTF and OTF will load from the data folder
• Render text with RGB then apply per-surface alpha when an RGBA color is provided, ensuring transparent fills/strokes composite correctly.
• Build stroke outlines via masks (subtract fill mask) so strokes don't appear inside glyph interiors when fill is transparent.
• Mirror behavior for OffscreenSurface, add/adjust type annotations, and fix indentation/flow issues.
• Tests & typing: all tests pass (110 passed, 2 skipped); mypy clean.

Related issues

N/A

Checklist

• I added tests covering the new behavior (or gave a clear reason why not).
• I ran mypy src/ locally and fixed type issues.
• I ran ruff check src/ tests/ and addressed any findings.
• I ran the test suite locally: pytest -q.
• I updated docs/ where user-visible behavior changed.
• If this is a migration from a monolithic module into a package, a compatibility shim that re-exports the public API is included and noted here.

For contribution guidance, see CONTRIBUTING.md and docs/package-style.md.

Additional notes for reviewers:

• Design decisions:
• Potential follow-ups: