[ndeloof]

- What I did

Add a bump-compose workflow that opens a pull request updating DOCKER_COMPOSE_REF in common.mk when a new Compose release is out, instead of someone doing it by hand each time (like #1356 or #1360).

• it starts on a bump-compose repository_dispatch event whose client_payload.version is the released tag, or manually (workflow_dispatch) with the version as input; the version is accepted with or without the v prefix, validated, and must be an existing tag of docker/compose;
• it does nothing when common.mk already packages that version, and an automatic dispatch never lowers the packaged version (a patch release of an older line is ignored); a manual run can;
• the pull request targets master, is created with a GitHub App token restricted to contents and pull requests, uses the usual title (bump compose to version vX.Y.Z), a signed and signed-off commit, and the changelog block of the pull request template.

Needs before it can run

• the DOCKER_READ_WRITE_APP_ID variable and DOCKER_READ_WRITE_APP_PRIVATE_KEY secret available to this repository, and the app installed on it;
• something sending the bump-compose event from the Compose release (not part of this PR); until then it can be run manually.

- Description for the changelog

Not user-facing (CI only).

🤖 Generated with Claude Code

[thaJeztah]

I'll check with @vvoland if this was still needed (we're really close to getting rid of this repository in our pipelines, so I'll wait merging for now).

[vvoland]

Not needed, we don't build plugins from this repo anymore. It's only for engine and cli on the 29.9 branch.
29.10 will use docker/packaging too.

IBM is still using it currently, but I think they sync these version on their own. Will check up with them.

But for Docker packages we don't need to update this repo