Table name already exists

[ahuang11]

LLM generated table name could be duplicate of previous and when recreating the eph table, it crashes:

  File "/Users/ahuang/repos/lumen/lumen/ai/assistant.py", line 482, in invoke
    await agent.invoke(messages[-context_length:], **kwargs)
  File "/Users/ahuang/repos/lumen/lumen/ai/agents.py", line 738, in invoke
    sql_query = await self.answer(messages)
  File "/Users/ahuang/repos/lumen/lumen/ai/agents.py", line 734, in answer
    sql_query = await self._create_valid_sql(messages, system, tables_to_source)
  File "/Users/ahuang/repos/lumen/lumen/ai/utils.py", line 47, in async_wrapper
    output = await func(*args, **kwargs)
  File "/Users/ahuang/repos/lumen/lumen/ai/agents.py", line 606, in _create_valid_sql
    raise e
  File "/Users/ahuang/repos/lumen/lumen/ai/agents.py", line 580, in _create_valid_sql
    sql_expr_source = source.create_sql_expr_source({expr_slug: sql_query})
  File "/Users/ahuang/repos/lumen/lumen/sources/duckdb.py", line 232, in create_sql_expr_source
    raise e
  File "/Users/ahuang/repos/lumen/lumen/sources/duckdb.py", line 217, in create_sql_expr_source
    self._connection.execute(table_expr)
duckdb.duckdb.CatalogException: Catalog Error: Table with name "top_5_winter_olympic_games" already exists