Add Quantum Carpet particle-in-a-box brush

[Fokiees]

Example

Summary

• add a deterministic quantumcarpet brush based on particle-in-a-box wave-packet evolution
• map transverse position across the stroke to the particle position and progress along the stroke to time
• expose controls for ribbon radius, eigenstate modes, evolution rate, blend strength, and color
• include a physics/creative-use README, generated before/after images, and focused unit tests

The brush uses interference between energy eigenstates with their characteristic
n^2 phase evolution, producing bright bands, dark canals, and partial revival
structures along a stroke. It depends only on NumPy at runtime.

Validation

• python -m unittest effect.quantumcarpet.test_quantumcarpet -v
  • 3 tests passed
• python -m effect.quantumcarpet.generate_examples
  • generated the committed before/after images from the actual brush
• python -m py_compile effect/quantumcarpet/quantumcarpet.py effect/quantumcarpet/generate_examples.py effect/quantumcarpet/test_quantumcarpet.py
• validated effect/quantumcarpet/quantumcarpet_requirements.json as JSON

AI disclosure

I used OpenAI Codex for repository navigation, implementation drafting, test
review, and submission preparation. I reviewed the implementation, inspected
the generated output, and ran the validation commands above locally.

Addresses #50.