Build materials and shaders as a data-driven system, not one-offs

Authoring a unique shader per material doesn't scale: it multiplies engineering work, fragments the rendering pipeline, makes optimization impossible, and locks artists out of their own materials [S-realtime-rendering]. A systemic approach — master materials exposing parameters, instanced and tuned per asset — is the data-driven-design principle (ARCH-0001) applied to rendering: behavior and variety live in editable data (material instances) that artists control, while the underlying shaders stay few and optimizable. This empowers content creators (CONTENT-0002) to author look variety without programmers, keeps the shader count (and thus rendering cost, TECH-0002) under control, and makes the material library consistent and maintainable. It's the same "build the seam, fill it with data" logic that runs through the architecture layer.