Exception types in `handlers.llm` should be narrower

[eb8680]

There are at least a couple places in #363 where we have exception handlers for the base Exception type. These should be narrowed so that the handlers don't capture things they shouldn't.

[jfeser]

• https://github.com/BasisResearch/effectful/pull/363/files#diff-85fb9e79af6bc98e96213bcfc5f3efef453f02a84361f7eab5161e4ffb799ddeR155
  • Handles exceptions raised during a tool call. The LLM is responsible for generating the tool arguments, so almost any exception could be raised here if the arguments are incorrectly formed.
• https://github.com/BasisResearch/effectful/pull/363/files#diff-f4b86f4d3edaf4d72bdf9e31b711e960ff0629476b16c29b0fb180cf4b296130R50
  • Handles exceptions raised while evaluating LLM-generated code. We could probably be stricter here if there are clearly some exceptions that indicate a failure in the application and not the generated code.