chore(skills): drop Eve-only agents/openai.yaml from authored grilling

omp's skill scanner ignores agents/*.yaml (Eve/Codex binding metadata
carried along by the skills CLI store). The file kept vanishing from the
live tree to a background sweep; an authored omp skill does not need it.
Refs #16

agent/skills/grilling/agents/openai.yaml

@@ -1,3 +0,0 @@
-interface:
-  display_name: "Grilling"
-  short_description: "Stress-test thinking a round of questions at a time"