offscale, extracted from the platform into its own repository

The tailnet plugin — machines, users, pre-auth keys, access policy and device
invites. Moved out of officerdev/platform, where it had lived in plugins/ since
the plugin system was built.

Until now this code existed in exactly one place: the platform repository. That
made "gitignore the plugins directory" impossible to do safely, because
untracking it would have left 49 files on a single disk with no remote. This
repository is what makes that move safe.

Same extraction as plugins/music before it: source only, no history. The
platform's history still holds every commit that shaped this, and the SHAs cited
across the codebase keep resolving — replaying it here would have created a
second, divergent account of the same work.

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

.gitignore

@@ -0,0 +1,2 @@
+node_modules/
+*.log