Cross-crate integration TODOs

Collected from agent reports; resolve during integration phases.

vt osc/parsers/semantic_prompt.rs: local printf-q / percent decoders → share with ghostty-os::string_encoding (vt can't depend on os; maybe move into vt and have os re-export).
os locale::ensure_locale no-op → call setlocale from apprt-gtk (unsafe allowed) at startup, as Ghostty's global.zig does.
os passwd Flatpak branch needs termio Pty.
os open::OpenUrlKind → replace with core apprt action type.
font sprite/face.rs: local Presentation/RenderOptions stand-ins → real font types (Phase 3).
font crate: re-add deps on config/unicode/terminal in Phase 3.
terminal crate: re-add deps on unicode/datastruct once those land.