Resolve conflicts with main:
- handler/grok_media_test.go: keep both new tests (schedule model test from
this branch, eligibility gating tests from #4540)
- service/openai_gateway_grok_test.go: keep both new tests; update the image
cases of the mapping table test to return a non-empty image payload because
#4497 (already on main) now converts empty image responses into an upstream
failover error
shaw
9d498c2474