Remove generated README files from docs/screens/realism and update the screens
index to treat realism as a gitignored local QA directory with no README gate.
Create an index README in docs/ and every tracked docs subfolder, with relative
image galleries for Blender previews, screen designs, screenshots and concepts.
Generated realism-run READMEs were also created on disk but remain gitignored.
Validate all Markdown/image links.
zwitschi