Verification
Use CLI smoke checks to validate provider access. This validates storage access, not UI upload behavior.
Safety boundary
Only create and delete objects under _vibecodemax/healthcheck/*.
supabase storage cp ./test.txt ss://<bucket>/_vibecodemax/healthcheck/production/<timestamp>/test.txt --linked --experimental
supabase storage ls ss://<bucket>/_vibecodemax/healthcheck/production/<timestamp>/ --linked --experimental
supabase storage rm ss://<bucket>/_vibecodemax/healthcheck/production/<timestamp>/test.txt --linked --experimental