CI: add a manual run to deploy from

Woodpecker only offers Deploy on a successful pipeline, and the tests can't
pass until the builder image exists, so nothing could start the first build.

README.md

@@ -246,6 +246,11 @@ click **Deploy**, and set the deploy target:
 `all` doesn't include `builder`. Rebuild the image after changing its
 Dockerfile, and before the first run of anything else.
 
+Woodpecker only offers **Deploy** on a successful pipeline, and on a repo with
+**Allow deployments** turned on. The tests can't pass until the image exists,
+so for the first build, or any time the newest push failed, click **Run
+pipeline** and use **Deploy** on that run (`.woodpecker/manual.yaml`).
+
 - **It publishes to the same place you do.** The pipeline mounts the release
   directory and its keys from the NAS at `/nfs/hal9000/mtgc`, then runs that
   directory's `update-repo.sh` to copy the public files out, so CI and a dev