Merge document identity mismatch

The ours and theirs inputs have different asset IDs or document kinds. The merge is rejected without producing a merged document; unrelated assets must not be combined as revisions of one document.

#Common causes

• Inputs from different scene or prefab files were supplied to ara merge.
• One side changed the document's asset ID or kind.

#Fixes

• Supply ara merge <base> <ours> <theirs> with revisions of the same asset.

• Restore an accidentally changed identity from the correct prior version; keep intentionally distinct assets as separate documents.

• Code: ARA1702

• Constant: MERGE_ID_MISMATCH

• Reported by: ara-merge