[Bug Report]: TransactionReceiptQuery with setIncludeChildren(true) returns empty children array for ATOMICBATCH transaction

As part of investigating the issue I created in the `hiero-sdk-js` https://github.com/hiero-ledger/hiero-sdk-js/issues/3859 [venilinvasilev](https://github.com/venilinvasilev) suggested that I should raise that issue here.

To make it brief the issue we are facing is that when using `TransactionReceiptQuery` from `@hashgraph/sdk` to fetch the receipt of an `ATOMICBATCH` transaction with `.setIncludeChildren(true)`, the returned `receipt.children` array is always empty, even though the batch transaction contains child transactions. More on the problem and steps to reproduce can be read in the mentioned issue's description,

`venilinvasilev` suggested in this [comment](https://github.com/hiero-ledger/hiero-sdk-js/issues/3859#issuecomment-4066203616) that the problem lies on the fact that for `ATOMICBATCH`, whether inner transactions should appear in `child_transaction_receipts` is a consensus-node/spec interpretation question.

Start by reading the linked hiero-sdk-js issue and its referenced comment, then trace TransactionReceiptQuery handling for ATOMICBATCH receipts and child_transaction_receipts in the consensus node. The expected behavior must first be resolved as a consensus-node/spec question; done means the agreed semantics are implemented and verified for setIncludeChildren(true).

Written by the indexing model from the issue text.