Local Libretro Specs

The spec/ directory contains local Markdown copies of upstream libretro docs used during implementation and review. Start from the index:

• spec/README.md

The current local references are:

• spec/input-api.md
• spec/developing-cores.md
• spec/dynamic-rate-control.md
• spec/opengl-cores.md
• spec/core-options-translation.md

These are reference documents, not replacement tutorials. Book chapters should summarize the workflow for this Rust API and link to the spec when the upstream libretro contract is the important source of truth.