New KEY_DIRS entry (index 12, same pattern as cuasSynth/cuasNoise):
SET casesFile <path> in a scene-sequence .list names the GPU-test case
manifest (tile_processor_gpu run_cases.sh reads the same SET). A FILE key:
exempt from the auto-mkdirs branch; resolved vs rootDirectory and recorded
in this.casesFile (informational for now - reserved for in-program use).
Parses cleanly instead of the '*********** Unknown SET' console warning.

Companion to tile_processor_gpu edc6c4a. mvn compile OK.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>