Add UAI format support for probabilistic inference (Issue #4)

This commit adds support for generating UAI (Uncertainty in Artificial
Intelligence) format files from detector error models, enabling
probabilistic inference with tools like TensorInference.jl.

Changes:
- Add dem_to_uai() to convert DEM to UAI format
- Add save_uai() to save UAI files
- Add generate_uai_from_circuit() for CLI integration
- Add --generate-uai flag to CLI
- Generate UAI files for all demo circuits
- Add comprehensive test coverage for UAI functionality

The UAI format represents the DEM as a Markov network where:
- Each detector is a binary variable
- Each error mechanism is a factor/clique
- Factor tables encode error probabilities

Addresses #4

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: ChanceSiyuan