Font discovery: enumerate and load system fonts #28

Phase 2: Pure Rust Font Engine#

Improve font loading to enumerate available system fonts and support loading by family name, rather than hardcoding paths to Geneva/Monaco.

Font discovery#

• Scan /System/Library/Fonts/ and /Library/Fonts/ directories
• Read font files and extract name table metadata (family name, subfamily)
• Build a font registry mapping family names to file paths
• Support .ttf and .otf file extensions
• Handle font collections (.ttc files) — parse the TTC header to extract individual font offsets

Font selection API#

• FontRegistry::new() -> FontRegistry — scans system font directories
• FontRegistry::find_font(family: &str) -> Option<Font> — load by family name
• FontRegistry::find_font_with_style(family: &str, bold: bool, italic: bool) -> Option<Font> — load with style preference
• FontRegistry::list_families() -> Vec<String> — list available font families

Fallback#

• Default fallback font if requested family not found
• Maintain a prioritized list: requested font -> system default -> any available font

Acceptance criteria#

• System font directories are scanned on initialization
• Fonts can be loaded by family name (e.g., "Helvetica", "Times New Roman")
• TTC collections are handled (extract individual fonts)
• Font registry lists available families
• Fallback works when requested font is not found
• All existing tests continue to pass
• cargo clippy --workspace -- -D warnings passes
• cargo fmt --all --check passes