## Summary
On every `main` build, once the webapp image is pushed to the registry,
the publish workflow emits a cross-repo `repository_dispatch` event
(`main-image-published`) carrying a digest-pinned image ref. Other
repositories in the org can subscribe to that event and build or deploy
from the exact artifact, instead of chasing the moving `main` tag.
## Design
`publish-webapp.yml` now exposes the pushed multi-arch index digest as a
workflow output. `publish.yml` adds a `dispatch-main-image` job (after
`publish-webapp`) that builds `<image_repo>@<digest>` and sends the
dispatch via the same pinned `peter-evans/repository-dispatch` action
already used elsewhere in this repo, authed with `CROSS_REPO_PAT`.
It fires only when the published tag is `main`, so semver releases and
other tag builds are excluded, and only from the canonical repo so forks
never dispatch. The payload is JSON-escaped with `jq`.
Matt Aitken
df964ea4ee