Summary

• Remove duplicate self.time: float = 0.0 assignment in Model.__init__
• Fix inverted warning messages in Model._advance_time() and Model.run_until() — the condition checks until <= self.time but the message said "is larger than" (should say "is not larger than")
• Fix DataCollector.get_model_vars_dataframe() and get_agent_vars_dataframe() — they used raise UserWarning(...) which crashes the caller instead of issuing a warning. Changed to warnings.warn() with a graceful return pd.DataFrame()
• Replace bare raise Exception(...) with raise ValueError(...) in add_table_row() and get_table_dataframe() for better exception specificity