[codex] Rename project identity to Bearshape

[acecchini]

Summary

• renames the source package, distribution metadata, imports, docs, examples, tests, typing fixtures, notebook, lock/config files, and release workflow to Bearshape
• rewrites README and CONTRIBUTING into concise project-facing guides
• keeps the rename clean: no compatibility package for the previous import identity

Validation

• uv --cache-dir .uv-cache sync
• import bearshape -> bearshape 0.0.1
• import bearshape.numpy -> bearshape.numpy
• previous import package lookup -> None
• old-name audit across project files, excluding .git, site, .venv, and .tox -> no matches
• uv --cache-dir .uv-cache run pytest -n auto tests/ -> 1063 passed, 5 skipped
• uv --cache-dir .uv-cache run pyright src tests/typing -> 0 errors
• uv --cache-dir .uv-cache run mypy src tests/typing -> no issues
• uv --cache-dir .uv-cache run ty check src tests/typing -> all checks passed
• uv --cache-dir .uv-cache run mkdocs build --clean
• uv --cache-dir .uv-cache run prek run -a
• uv --cache-dir .uv-cache run tox run -e dev -> 1063 passed, 5 skipped, coverage 91.20%
• uv --cache-dir .uv-cache build -> built dist/bearshape-0.0.1.tar.gz and dist/bearshape-0.0.1-py3-none-any.whl

PyPI

• Local package metadata, uv.lock, built artifacts, and trusted-publishing workflow now target bearshape.
• No live PyPI publish was run. Publishing waits for review, merge, tag, and explicit approval.

Notes

• CuPy runtime validation remains deferred until a CUDA GPU environment with CuPy is available.