Add few-shot prompt support with zero-shot/few-shot distinction

[MHindermann]

Add support for few-shot prompts based on experiments from https://github.com/kintopp/dspy-rise-humbench.

Requirements:

• Implement few-shot prompt templates/examples
• Add mechanism (flag, rule, or metadata field) to distinguish zero-shot vs few-shot tests
• Ensure test results clearly indicate which prompting strategy was used

Performance consideration:
Few-shot prompts (especially with images) are ideal candidates for context caching to reduce API costs and latency on repeated runs.