* feat(odm): merge the source listing into ListObjectsV2
Adds policy.list_through: ListObjectsV2 merges the local and source
listings into one ordered page so clients see the whole namespace during
an on-demand migration. Local entries win a key both sides hold,
CommonPrefixes are unioned under a delimiter, and the continuation token
is an opaque versioned envelope carrying both cursors.
A source listing failure or an open breaker follows policy.source_error:
propagate answers 424, not_found answers from local state and marks the
response x-rustfs-on-demand-migration-list: local_only. Source listings
are capped at 10 per second per bucket.
* test(odm): refresh the e2e-full darwin selection digest
The list-through e2e module adds seven cases to the merge lane.