[Bug]: RetrieverEvaluator, MultiModalRetrieverEvaluator and ObjectRetriever.aretrieve still call sync postprocess_nodes() in async paths

Finding: In llama-index-core 0.14.25 (main @ 7e2c60a), per the reporter, the async paths RetrieverEvaluator._aget_retrieved_ids_and_texts, MultiModalRetrieverEvaluator._aget_retrieved_ids_and_texts and ObjectRetriever.aretrieve still call the sync postprocess_nodes() rather than awaiting apostprocess_nodes() (https://github.com/run-llama/llama_index/issues/23326). This is an external report only; KFA has not reproduced it. Context reported in the issue: an earlier change (#20974, for #20973) switched chat engines, CitationQueryEngine, SimpleMultiModalQueryEngine and RetrieverTool to the async postprocessing call, but reportedly did not touch these three call sites. The reporter says the triage comment on #20973 had already listed them as affected (https://github.com/run-llama/llama_index/issues/23326). Symptom: no exception is raised; the sync path is used silently. The reporter's script uses a tracking postprocessor that records whether the sync or async method ran. They report that aevaluate() on RetrieverEvaluator and aretrieve() on an ObjectIndex retriever both recorded only 'sync', where 'async' was expected. They state MultiModalRetrieverEvaluator.aevaluate behaves like RetrieverEvaluator (https://github.com/run-llama/llama_index/issues/23326). Reported consequences: postprocessors with native async implementations (LLMRerank, StructuredLLMRerank, RankGPTRerank) never use them from these paths. The reporter also argues an LLM-based reranker would make a blocking sync call on the event loop, serializing concurrent aevaluate()/aretrieve() calls. This second point is the reporter's reasoning, not shown by a supplied timing measurement (https://github.com/run-llama/llama_index/issues/23326). Diagnosis hint (reported, not verified): if you use async evaluation or ObjectRetriever.aretrieve with node postprocessors on this version, a postprocessor's async method may not be invoked. A custom postprocessor that records which method ran, as in the issue, would show this. Status: the reporter proposes changing the three call sites to await apostprocess_nodes() with the existing arguments, and notes the base class falls back to asyncio.to_thread for postprocessors without native async support. A commenter with no stated association said they would open a PR (https://github.com/run-llama/llama_index/issues/23326#issuecomment-5943018462). No maintainer response, merged fix or released fix appears in the supplied sources. Other versions are unknown. No workaround is stated. Limitations: single AI-drafted external report; comments may be incomplete; no independent reproduction; the fix is a proposal only and is not confirmed or shipped.