Tag and publish first beta

[Zhortein]

Objective

Tag and publish the first beta release.

Target version

v0.3.0-beta.1

Scope

• Ensure develop is ready.
• Merge or fast-forward main to develop.
• Create the tag.
• Push the tag.
• Verify GitHub release workflow.
• Verify GitHub release notes.
• Verify Packagist update.
• Optionally test installation from Packagist.

Acceptance criteria

• main contains the release state.
• Tag v0.3.0-beta.1 is pushed.
• GitHub release exists.
• Packagist sees the new version.
• Installation test succeeds if performed.