Search for entities across multiple types using the Open Targets Platform search API.

    This tool performs a streamlined entity search that returns the id and entity type
    for up to 3 matching entities across targets, diseases, drugs, variants, and studies.

    Supports multiple query strings in a single call - each query is executed independently
    and results are returned in a dictionary keyed by the query string.

    Args:
        query_strings: List of search queries (e.g., ["BRCA1", "breast cancer", "aspirin"])

    Returns:
        dict: Dictionary mapping each query string to its results (array of up to 3 entities
              with id and entity fields), or error message if any query fails.

    Example:
        Input: ["BRCA1", "aspirin"]
        Output: {
            "BRCA1": [
                {"id": "ENSG00000012048", "entity": "target"},
                {"id": "EFO_0000305", "entity": "disease"}
            ],
            "aspirin": [
                {"id": "CHEMBL25", "entity": "drug"}
            ]
        }