Pin remaining --all-refs paths: incremental relay, batched bootstrap, replicate

Three tests cover the paths that were left implicit:

• IncrementalRelayWithBranchOnlyPush: source has a notes ref already current on target, branch needs an update. AllRefs broadens the ref discovery, but pushPlans is branch-only so CanIncrementalRelay accepts. Asserts the relay path engages (RelayMode=incremental) rather than getting tripped up by the broader scope.

• BatchedTailPhase: large-blob source forces TargetMaxPackBytes batching on bootstrap. The notes ref on source has to ride the renamed tail-phase (was tag-phase) of executeBatched. Asserts both that the batched mode engaged and the notes ref landed at the right hash.

• ReplicateRejectsOtherKindIntoExistingTarget: replicate's relay-only push gates on CanReplicateRelay which rejects RefKindOther. The test pins this as a deliberate v1 limitation: replicate + AllRefs other refs into a non-empty target errors with "use sync instead" rather than silently doing the wrong thing. (Empty-target replicate works via the bootstrap path, which is already covered.)