graph-agents-cli 0.3.1

0.3.1 is the first release published on PyPI.
Its commands and templates are 0.3.0's (only the version, the documentation, the skills'
install lines and the release workflow change), so a project created by 0.3.0 needs no
migration.

Changed

• Published on PyPI. Install with uv tool install graph-agents-cli (or pipx install graph-agents-cli); the release tag git+https://github.com/ss7172/graph-agents-cli@v0.3.1
  installs the same release. 0.3.0 and earlier stay on their git tags only.
• The README and the documentation point to PyPI: the README's install section (with a
  PyPI badge), the site's Installation page, announcement bar, home page and tutorials, and
  the workflow and scaffold skills' install lines. "Not on PyPI yet" is gone. setup,
  update, the scaffold upgrade baseline and generated projects' GRAPH_AGENTS_CLI_SPEC
  still install from the release tag, since earlier releases exist only as tags;
  GRAPH_AGENTS_CLI_INSTALL_SPEC='graph-agents-cli=={version}' switches them to PyPI.

Fixed

• The release workflow's GitHub Release job is idempotent. A second run for the same
  tag (GitHub started two for the v0.3.0 push, and the second failed with "a release with
  the same tag name already exists") now finds the release, uploads only the assets it lacks
  and never replaces one; the PyPI job skips files already on PyPI.