Summary

• NumPy 1 compatibility — replace np.acos / np.asin / np.atan2 (NumPy 2.0+ aliases) with np.arccos / np.arcsin / np.arctan2 in interpolatepy/quat_core.py, so the package runs on the NumPy 1.x line again.
• Relax runtime floors in pyproject.toml: numpy>=1.26, matplotlib>=3.6, scipy>=1.11 (was numpy>=2.3.0, matplotlib>=3.10.5, scipy>=1.16.0). Version bumped to 3.0.1.
• Migrate dev tooling to uv: workflows (test, docs, pre-commit, publish) now use astral-sh/setup-uv@v6 + uv sync --locked; pyproject.toml switches [project.optional-dependencies] → [dependency-groups] with default-groups = ["dev", "test"]; CI passes --no-default-groups --group <name> to install only what each job needs. pre-commit.yml adds a ~/.cache/pre-commit cache with a restore-keys: fallback. uv.lock and .python-version are now tracked. Docs (README.md, docs/installation.md, docs/contributing.md, docs/troubleshooting.md) updated to the uv-based contributor flow.
• Drive-by: fix codecov-action@v5 input — file: → files: (caught by actionlint).

Test plan

• uv sync --locked --no-default-groups --group test then uv run pytest tests --cov=interpolatepy — 739 passed, 4 skipped (~60 s, local).
• uv sync --locked --no-default-groups --group docs then uv run mkdocs build --clean --strict — built clean.
• uv sync --locked --no-default-groups --group dev then uv run pre-commit run --all-files — all hooks pass (ast, types, merge-conflict, yaml, toml, ruff, mypy).
• uv build + uvx twine check dist/* — wheel + sdist both PASSED.
• actionlint clean across all 4 workflows.
• CI matrix on push (Ubuntu + macOS × Python 3.11/3.12/3.13).
• Codecov upload succeeds with the corrected files: input.
• Docs Pages deploy on main.