fix: defer KG rebuild during batch document deletion

[danielaskdd]

Fixes an issue where batch document deletion causes redundant N Knowledge Graph rebuilds. It introduces a skip_rebuild flag to adelete_by_doc_id(), allowing batch deletion processes to defer per-document KG rebuilds. Rebuild data (entities, relationships) is returned from deletion and aggregated by the caller. It incorporates the logic from PR 2819 and includes additional checks to ensure fully deleted entities and relationships are not rebuilt with stale data. Adds tests to cover this optimization and its edge cases.

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PR created automatically by Jules for task 16849260015452852282 started by @danielaskdd

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