Publish cli package to pypi

[SirEntropy]

Why are these changes needed?

Adds the release pipeline and PyPI metadata for publishing ag2-cli as a standalone package.

Changes

• .github/workflows/cli-package.yml — New GHA workflow that builds and publishes ag2-cli to PyPI. Triggers on releases tagged cli-v* (e.g. cli-v0.1.0) or manual dispatch. Uses the existing package environment and PyPI credentials.
• cli/pyproject.toml — Added project.urls (Homepage, Docs, Source, Tracker, Discord), keywords, and classifiers so the PyPI page has proper metadata and sidebar links.

Release process

1. git tag cli-v0.1.0 && git push origin cli-v0.1.0
2. Create a GitHub release from the tag
3. Workflow builds from cli/ and uploads to PyPI

The cli-v* tag prefix keeps CLI releases independent from the main ag2 package (v* tags).

Checks

• I've included any doc changes needed for https://docs.ag2.ai/.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
see 62 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.