Silent JSON parsing errors in the app

[caufieldjh]

Some JSON parsing errors yield empty results in the app but don't raise an error, so it's unclear to the user what happened.

For example, when running the Extract function with a database of VBO and sending the string "The Zwartbles is a breed of sheep." to GPT-4o with no background generation, the error on the command line is this:

Could not parse ```json
{
  "id": "Zwartbles_Sheep_",
  "label": "Zwartbles (Sheep)",
  "definition": null,
  "aliases": null,
  "relationships": [
    {
      "predicate": "subClassOf",
      "target": "IndependentContinuant"
    },
    {
      "predicate": "subClassOf",
      "target": "SheepBreed"
    }
  ],
  "logical_definition": null,
  "original_id": "VBO:0010001"
}

But the extracted object is empty ( {}).

[caufieldjh]

Ah, I thought I had fixed this before, but #54 only fixes the MappingAgent, not any of the extraction functions. So the JSON/Markdown processing should probably be more of a general utility.