Add a Slang module

1. Give the file a module declaration matching its search-path identity.

2. Export only the functions/types consumers need.

3. Put project modules on a Slang search path; reserve miskeyed.* for packaged Workbench contracts.

4. Import it normally and verify it appears in Dependencies.

module studio.color;
public float3 grade(float3 c) { return pow(c, 1.0 / 2.2); }

Workbench should not gain a second resolver for this extension.