Add docs/RELEASE.md, linked from README.md's Release Artifacts section, giving
the release procedure as a numbered list: confirm main is green in CI, confirm
the one version in package.json and the two manifests matches the intended tag,
make package from a clean checkout, verify SHA256SUMS, create the annotated tag
vX.Y.Z, then distribute per browser. Each step names who performs it, marks the
owner-only ones, and states the check that it worked. Every repo command cited
(make setup, make check, make package) exists on next; tagging and verification
use standard git and coreutils, and the CRX pack line is README's own.
The per-browser distribution step is written as pending the owner's choice on
issue 386, with the Firefox and Chrome options named but none presented as
settled. Docs only: no code or test changes.
Model: opus-4-8
