[Prompt Engineering] Include method/function definitions for code near the cursor

Hypothesis: The LLM will do a lot better if we include the function/method prototypes for the current code that we're working on. For example, let's suppose the user's prompt were this:

    def enqueue_batch(batch, index)
      job = enqueue!(

If we were able to find and provide the definition of enqueue!, that might help the LLM auto-complete this better:

    def self.enqueue!(uploads, to_store)
      perform_async(uploads.ids, to_store)
    end

Often the method/function might be defined in another file, so having multiple files and/or an indexed database would probably be more effective for method lookup. However, we can demonstrate that if the definition is in the same file, we can create better prompts.

Proposal:

1. Run the code through TreeSitter.
2. Attempt to identify all function/method prototypes.
3. Try to find a match for the given call.
4. Augment the prompt with that definition, commenting out code if necessary.