Harden 0.7.0 release cutover and refresh agent context

[JovaniPink]

Summary

This PR folds the final 0.7.0 release-cutover cleanup into master through a reviewable branch instead of leaving the work as direct commits.

What Changed

• Hardened the GitHub Release publish workflow:
  • run only for non-draft, non-prerelease GitHub releases
  • use explicit read-only repository permissions
  • serialize release publishes by tag with a concurrency group
  • fetch full history so release tags can be compared against origin/master
  • verify the release tag matches the package version in pyproject.toml
  • verify the release tag points at the current origin/master
  • fail early when PYPI_TOKEN is missing
• Updated release-facing docs for 0.7.0:
  • README installation now points to pip install xstate
  • CHANGELOG records the release workflow hardening and PyPI-facing install docs
• Refreshed agent context:
  • removed stale PyPI-pending language from AGENTS.md
  • cleaned up duplicate and stale module entries in CLAUDE.md
  • restored the documented ruff format --check command for format verification

Why

The release path needed a few guardrails before PyPI publishing: the workflow should only publish the intended final release tag, it should prove the tag matches the packaged version and current master, and it should fail clearly if the upload token is not configured.

The agent context also needed to match the post-cutover repository state so future automation does not work from stale release assumptions or duplicated architecture notes.

Validation

• Inspected the exact diff from ed8c0ce to b6f0ce8 before opening this PR.
• Confirmed the PR branch contains the two intended commits only:
  • 4ac8901 Harden 0.7.0 release publish cutover
  • b6f0ce8 Refresh agent context after release cutover
• No local test suite run: changes are limited to documentation and GitHub release workflow configuration.

[gemini-code-assist]

Code Review

This pull request prepares the repository for the 0.7.0 release. It updates the documentation (AGENTS.md, README.md, CLAUDE.md) to reflect the release status, updates the installation instructions to use PyPI, cleans up the file structure list in CLAUDE.md, and adds a --check flag to the formatting command. Additionally, the CHANGELOG.md is updated with details about the hardened GitHub Release workflow and PyPI installation docs. There are no review comments, and I have no additional feedback to provide.

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