The remediation ("set compression.checkpoint_required: false, or switch
provider") is right only when the gate can never pass with the active provider
set. Attached to every _checkpoint_blocked() it also decorated the transient
"provider checkpoint API v2 failed" path, where the provider IS capable and the
correct move is a retry once the store recovers, and the codex_app_server
refusal, where switching memory provider changes nothing. A small
_checkpoint_incapable() wrapper carries it on the two capability branches only.
Tests: six near-duplicates collapse into three invariants (warn on mismatch,
parametrized over v1 provider / no manager; silent when off or capable; the
compress-time refusal names the flag). Proven red with the fix neutralized.
Consolidates #106879 (KoNit-K) and #106882 (kokhlo); fixes#106870.
96030a3536