offscale moves to its own repository

Pushed to gitea.officer.dev/plugins/offscale (50 files, verified byte-identical
to the working copy by cloning it back), then untracked here.

Order matters and it was this way round deliberately: until that push, this
repository was the only copy of those 49 files. Untracking first would have left
them on one disk. The push is what made the removal safe, so it happened first
and was verified before anything was removed.

The files stay on disk and the installed plugin keeps working — this changes who
owns the code, not what is running.

`example` stays tracked, alone. It has no repository yet, and it is the reference
implementation EXTRACTING-A-PLUGIN.md sends people to read; removing it would
both delete it from everywhere but this disk and leave the doc pointing at
nothing. It follows once it has a remote.

Not done, and worth knowing before a fresh install: plugins/offscale is PRIVATE,
and fetch.ts clones anonymously over https with no credentials by design. So
offscale cannot be installed from the marketplace the way music can. It needs to
be public, or the marketplace needs authentication — which is a feature, not an
oversight to patch quietly.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

.gitignore

@@ -105,5 +105,7 @@ src/databases/officer_db/migrations/
 # deliberate act, so keeping this list by hand is the right amount of friction — an unlisted plugin
 # directory is an install, not a source file.
 /plugins/*/
+# `example` is the only exception left, and only until it has a repository of its own. It is the
+# reference implementation EXTRACTING-A-PLUGIN.md sends people to read, and it has no remote — the
+# platform repo is its single copy, so untracking it would delete it from everywhere but this disk.
 !/plugins/example/
-!/plugins/offscale/