Adopt the release-branch publishing model (ADR 0012 + config)

[arbrandes]

Description

Adopt the release-branch publishing model for frontend-base, both in the decision record and in the release configuration.

The ADR change amends section 3 of ADR 0012: the current stable is published from a long-lived release branch, which is a true release branch (it owns the npm latest dist-tag and can originate a major's first stable release), while n.x branches are retained for maintaining superseded majors, cut from release once the next major ships. A short note records why: semantic-release classifies any N.x-named branch as a maintenance branch, which can only patch an already-shipped major, never originate one.

The config change puts that model into effect. The branches config publishes the current stable from release (npm latest) and -alpha prereleases from main (the alpha dist-tag), replacing the placeholder entry and dropping channel: latest from main. The release workflow triggers on both main and release, keeping the configuration byte-identical on both branches.

Note on merge order: do not merge until the release branch has been cut and published. Until a release branch exists on the remote, main's release workflow would fail with ERELEASEBRANCHES, because the config references a release branch that is not yet present. The release branch is created as part of #244.

Closes #273.

LLM usage notice

Built with assistance from Claude.