docs/RENDER_THREAD.md: the record/replay model, why guest-visible VRAM
stays gpu.c's array (private upload source on the render thread), the
guest state captured at record time, every sync point with file:line,
the frame bound and present skipping, interoperation with savestates,
netplay, render passes, interpolation, widescreen, resolution changes,
screenshots, headless and Vulkan, what is out of scope, and the tests.
TCP_COMMANDS.md documents render_thread (index regenerated);
config_schema.md documents [video] render_thread.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Shokunin