Implement heuristic prompt factorization for parallel execution

Add a Factor operation to the free monad (Omni/Agent/Op.hs) that decomposes prompts into parallelizable sub-tasks.

Approach

Use an LLM to analyze a prompt and identify independent sub-tasks that can run in parallel. Not principled Bayesian factorization, but practically useful.

Prior Art

• ParallelPrompt benchmark (arxiv.org/abs/2506.18728) - measures intra-query parallelism
• Skeleton-of-Thought - generates outline then fills in parallel

Implementation

1. Add Factor constructor to OpF 2. Implement factorization prompt that identifies independent sub-tasks 3. Return list of sub-prompts that can be passed to existing Par combinator

Metrics & Verification

• Latency improvement vs sequential execution
• Output quality preservation (embedding similarity to sequential output)
• False independence rate (sub-tasks that actually depend on each other)

Test Cases

• Research tasks: 'Compare X and Y' -> [research X, research Y] -> combine
• Code tasks: 'Implement A, B, C' -> parallel if independent
• Analysis tasks: 'Review these 5 files' -> parallel per file

Notes

This is heuristic. True conditional independence detection in NL is a research problem. But even imperfect factorization helps.