[Bug]: RecursiveRetriever incorrectly converts zero scores to 1.0

Finding: In an external report against llama-index-core 0.14.25, RecursiveRetriever reportedly returns a resolved child node with score 1.0 when the parent IndexNode's NodeWithScore score is 0.0, instead of preserving 0.0 (https://github.com/run-llama/llama_index/issues/23429). This is an external report; KFA did not reproduce it. Reported symptom and environment: The reporter says the package was installed from PyPI as llama-index-core==0.14.25. No Python version or OS is given. A minimal script defines a BaseRetriever subclass that returns one NodeWithScore wrapping an IndexNode (index_id 'child') with score=0.0. A RecursiveRetriever with root_id 'root' and a node_dict mapping 'child' to a TextNode then retrieves. The reporter says the output score is 1.0 and the text is the child content. The expected score is 0.0. No exception is raised; the problem is silent score propagation (https://github.com/run-llama/llama_index/issues/23429). Reported cause (unconfirmed): The reporter attributes this to the expression 'score or 1.0', which treats 0.0 as falsy so both None and 0.0 become 1.0. They say the same pattern appears in RecursiveRetriever and in the synchronous and asynchronous expansion paths of BaseRetriever. This is the reporter's diagnosis. No maintainer has confirmed it in the supplied data, and it was not checked against source code here (https://github.com/run-llama/llama_index/issues/23429). Potential impact (reporter's claim): An inflated score could affect downstream ranking or score-based filtering, since a zero-relevance result would look maximally relevant (https://github.com/run-llama/llama_index/issues/23429). Status: The issue was open at the as-of time with no maintainer response visible. The reporter proposes replacing the expression with 'score if score is not None else 1.0' so only a missing score defaults to 1.0. This is a proposal only. No fix commit, pull request or release was supplied, so no fixed version can be stated. The one comment on the issue could not be retrieved, so it may contain relevant information. Practical reading: If you depend on zero scores through IndexNode expansion in 0.14.25, check the scores your retriever returns with a small test like the reporter's. Treat the cause as plausible but unverified until a maintainer or fix commit confirms it. Limitations: external report only, no KFA reproduction, no independent reproduction evidence available, and no confirmed fix or workaround.