docs(image): document Docker image naming mismatch

Add OCI title/description labels to the Dockerfile, note the
docker.gitea.com/gitea-mcp-server vs gitea-mcp naming mismatch in each
README with a link to a new docs/adr note recording the maintainers'
preferred gitea/mcp-server direction from issue #181, and add a test
that keeps the README image references consistent.

Co-Authored-By: Codet <codet@commitgo.dev> (GPT-5-Codex)

docs/adr/docker-image-naming.md

@@ -0,0 +1,29 @@
+# Docker image naming mismatch (issue #181)
+
+## Current state
+
+The project repository is `gitea.com/gitea/gitea-mcp`, but the Docker image is
+published as `docker.gitea.com/gitea-mcp-server`. This mismatch was raised in
+[issue #181](https://gitea.com/gitea/gitea-mcp/issues/181).
+
+## Maintainers' direction
+
+Per the issue discussion, the maintainers' preferred long-term name is
+`gitea/mcp-server`, matching the naming scheme used by `gitea/act_runner`
+(published as a `runner`-style short name) and by comparable projects such as
+`github/github-mcp-server`. The name `mcp-server` was preferred over
+`gitea-mcp-server` because the repository is primarily run as a local client
+process, not a traditional long-running server.
+
+## Decision
+
+No rename has happened yet; the discussion was explicitly left open in the
+issue. The current image name, `docker.gitea.com/gitea-mcp-server`, remains in
+use so that existing user configurations and documentation keep working.
+`org.opencontainers.image.title` and `org.opencontainers.image.description`
+labels were added to the `Dockerfile` to make the image self-describing
+regardless of the tag it is published under.
+
+If the image is renamed in the future, update the `docker.gitea.com/gitea-mcp-server`
+references across `README.md`, `README.zh-cn.md` and `README.zh-tw.md` together
+with this document.