🔧 Prepare project metadata for PyPI publication

[dariocazzani]

What does this PR do?

Fills in the project metadata required to publish devol to PyPI and begins the transition from a GitHub-only research codebase into a well-behaved Python package. This is the low-risk foundations batch — no behavior changes, no dependency restructuring, no release automation yet. Each follow-up phase (dep split, CI matrix, release workflow, README visual) will ship as its own PR.

Details

• Add LICENSE (MIT) with dual-author copyright for Dario Cazzani and Aleksandr Yeganov
• Add CHANGELOG.md following the Keep-a-Changelog format with [Unreleased] and [0.1.0] sections
• Add CONTRIBUTING.md covering dev setup, pre-PR checks, and expectations
• Add src/devol/py.typed marker so downstream type checkers pick up the package's inline hints
• Fill in pyproject.toml project metadata: readme, license, license-files, authors, keywords, classifiers, urls
• Move pytest from the required dependency list into the dev extra where it belongs
• Add docs/superpowers/ to .gitignore to keep local working notes out of git

Verification

• uv build succeeds, producing both wheel and sdist
• twine check passes on both artifacts
• py.typed and LICENSE ship inside the wheel
• Rendered METADATA shows the new authors, classifiers, URLs, and SPDX license expression
• All 15 existing tests pass

Out of scope (follow-up PRs)

• Dependency split (moving torch, gymnasium, etc. to the examples extra)
• Python matrix upgrade and CI job split
• master → main branch rename
• Release workflow with Trusted Publishers (OIDC)
• README visual (denoising trajectory figure + GIF)