feat(fallbacks): expose synthetic face sources

[caio-pizzol]

Adds a compact face-source model so a renderer can distinguish real fallback faces from reviewed synthetic ones without inferring from file coverage.

Why:

• some reviewed substitutes have one real face but can still cover requested styled faces through deliberate synthesis
• faces remains real face coverage, while face-aware lookups expose a synthetic render instruction for the requested face
• Cooper Black -> Caprasimo is the first safe migration: Regular stays metric-safe, styled synthetic faces are visual-only

Verified:

• bun run check
• git diff --check
• public-safety scan for local paths and internal terms