chore: announce the rename from the image itself, and stop rebuilding

[Taure]

Step one of retiring this image. Merging this publishes the final build.

What it does

Prints a deprecation notice on every start, then execs the node unchanged:

========================================================================
 ghcr.io/widgrensit/asobi_lua has been renamed.

   Use:  ghcr.io/widgrensit/asobi

 Change the image name in your compose file or manifest. Nothing else
 changes - same tags, same ports, same environment variables.

 THIS IMAGE IS NO LONGER REBUILT. Tags already published keep working
 and are not going away, but they will not receive fixes.
========================================================================

Why a notice rather than just stopping

The risk in retiring a tag is silence. Stop publishing and :latest freezes wherever it is; nothing fails, nobody is told, and people quietly stop receiving fixes while pulling a tag they believe is current. Saying it in the logs of every start is the one place an operator reliably meets it.

Verified, not assumed

• The notice prints and the node still boots behind it (130 supervisor progress lines).
• docker stop exits 0 in 5 seconds, not after the timeout - inserting a shell in front of tini has not broken signal propagation, which is the real risk of this change and would have shown up as hanging rolling deploys.

What happens next, in order

1. Merge this. It publishes the last asobi_lua build, now self-announcing.
2. A second PR removes docker-publish.yml, so nothing new is built.
3. The repo is archived.

The GHCR package is never deleted. Every tag already published stays pullable indefinitely - anyone pinned to a version keeps working forever. What stops is new builds.