Currently, WiredTiger does not explicitly prevent building overflow keys or values when a btree has the WT_BTREE_DISAGGREGATED flag set. In the disaggregated world the btrees should never allow overflow items. To enforce this constraint, we should add assertions in the reconciliation logic to catch such cases during development and testing.

Proposed Change:

• Add an assertion to ensure no overflow key or value is created if the btree is flagged as WT_BTREE_DISAGGREGATED.