Rename PyPI distribution to atlas-cognitive-memory

[RichSchefren]

Summary

• change the public Python distribution name from atlas-core to atlas-cognitive-memory
• preserve the atlas_core import package and atlas CLI
• update optional-install examples and remove an ambiguous README reference
• add regression tests for distribution metadata, version mapping, and CLI entry point

Verification

• ruff check atlas_core tests benchmarks scripts
• pytest tests/unit -q — 380 passed
• wheel and sdist built as atlas_cognitive_memory-0.1.0a1
• twine check passed for both artifacts
• clean wheel install verified atlas_core, version 0.1.0a1, and atlas --help

PyPI state

atlas-cognitive-memory returned 404 from the PyPI JSON API immediately before this change, so it is currently unclaimed. It will not be reserved until the first authenticated publication; issue #24 should remain open until that upload and a real pip install atlas-cognitive-memory verification succeed.