the design doc moves into the plugin it produced

docs/offscale-plugin.md becomes plugins/offscale/PLUGIN.md. most of it is about
the plugin system generally rather than about offscale, which is exactly why it
belongs with the worked example — the reasoning is most useful beside the code
it produced, and the platform's docs should not carry the history of something
it no longer knows exists.

every reference updated.

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

src/servers/plugins/manifest.ts

@@ -10,7 +10,8 @@
 // the tile is `{ label, icon, color, to: mountPrefix() }` and the title is `label`, all of which are
 // already below. Writing them twice could only ever drift.
 //
-// See docs/offscale-plugin.md for the reasoning behind each decision recorded here.
+// The reasoning behind every decision here is recorded in plugins/offscale/PLUGIN.md — the worked
+// example, kept next to the plugin it produced rather than in the platform's docs.
 
 /**
  * A permission the plugin adds to the platform's permission system.
@@ -34,7 +35,7 @@ export type PluginPermission = {
   //
   // Finer visibility — whose rows a member sees, what a read means for this plugin's data — is the
   // PLUGIN's business and lives in its own queries. The platform's answer is uniform: read, write, or
-  // nothing. See docs/offscale-plugin.md.
+  // nothing. See plugins/offscale/PLUGIN.md.
   /**
    * Requests that look like writes and are not — `POST /ssh-test` probes, `POST /policy/assist` proposes
    * a document and never saves one. Without declaring them, a read-level account meets what reads as a