feat: F5.3b the editor on a project of server F

?project=<uuid> opens the shared document over /sync and the room over
/sim (RemoteSimHost: messages wait for the socket, a lost socket comes
back with what it watched, F's refusal or parting ends it); instead of
the editor, a word why when F refuses or lets go. F tells each
connection its access at once. Who only reads sees everything and
changes nothing: no palette or undo, a locked surface, the sheet's
fields disabled (tabs stay), no starting or stopping; thawed, the
document comes anew. The toolbar names who started the simulation.
Refusals carry no message, so Hocuspocus writes nothing outside F's
JSON log. A browser test runs three people against a real F.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/editor/package.json

@@ -9,6 +9,7 @@
     "build": "vite build"
   },
   "dependencies": {
+    "@hocuspocus/provider": "3.4.4",
     "@mdg-filius/core": "0.0.0",
     "@mdg-filius/doc": "0.0.0",
     "@mdg-filius/fls": "0.0.0",