Adds a FreeType-based Discover implementation for Windows that walks the system (C:\Windows\Fonts) and per-user (%LOCALAPPDATA%\Microsoft\Windows\Fonts) font directories, matching descriptors via family_name / SFNT name table and optionally codepoint presence. Wired up as a new .freetype_windows backend which Backend.default() now returns on Windows. Existing freetype-only paths are untouched. With this in place, standard code paths -- +list-fonts, SharedGridSet font-family lookup, CodepointResolver fallback -- work on Windows without any os.tag == .windows branches in the caller. Co-authored-by: Claude <noreply@anthropic.com>