P1 of the SetDisks split (tracking backlog#815, depends on P0 backlog#816).
Give the Heal operation family its own module home: relocate set_disk/heal.rs
to set_disk/ops/heal.rs and move the HealOperations storage-api contract impl
beside its inherent helpers. The contract stays implemented for SetDisks so its
associated-type bounds are unchanged (ecstore_contract_compat_test still
covers it).
Method bodies are moved unchanged. The four inherent helpers widen from
pub(super) to pub(in crate::set_disk) to preserve their exact prior visibility
from the deeper module. get_pool_and_set now reads topology through
SetDisksCtx to keep the Heal family aligned with the P0 borrow pattern; the
read is provably identical (ctx.format()/pool_index() alias the core fields).
Runtime behavior is unchanged.
Zhengchao An