House and Street Trade Matching

You are given two lists of trade strings called house_trades and street_trades. Each trade is represented as a comma-separated string with four fixed-width fields: Symbol (4 alphabetical characters, left-padded with spaces), Type ("B" or "S"), Quantity (4 digits, left-padded with zeros), and ID (6 alphanumeric characters). Two trades form an exact match when all four fields are identical. Your task is to implement a function that returns all unmatched trades from both lists after all possible exact matches have been removed. If a trade appears multiple times, each occurrence is treated as a distinct trade; for example, if a trade appears twice in house_trades and once in street_trades, one will be matched and one will remain unmatched. The returned list must be sorted alphabetically.