Disabling cluster.routing.allocation.disk.threshold_enabled does not clear a
cluster already in flood stage: it keeps cluster.blocks.read_only_allow_delete
and every write returns 403 index_create_block_exception (run 389046, still red
after the previous fix). Clear that block explicitly on every attempt, set the
threshold off at boot, and print the probe/settings bodies for future triage.
Verified locally against opensearch:2.11.1: read-only block -> 403, then
PUT {... read_only_allow_delete: null} -> index creation 200.
admin