Search for Safety Data Sheets (SDS) by chemical or product name.

Args: chemical_name: Chemical or product name to search for, e.g. "Acetone". is_contains: If True, match names containing this text instead of requiring an exact match (useful for partial or misspelled names). include_synonyms: If True, also match known synonyms of the chemical name. limit: Maximum number of results to return (the source can return 100+ matches for common chemicals, so this keeps responses manageable).

Returns: A list of matching records, each with: id, product_name, manufacturer, cas_number, msds_number, revision_date, has_sds, and sds_url (a direct link to the SDS document, usually a PDF).