gitea: gate and judge every trunk the gate's source names, not main alone

The operator, 2026-10-28: the gates and trunk_rule apply to every trunk,
the branches the mesh installs from, and later there may be more than
main. The trunks are read at the call from mesh-delivery-gate's source,
in one function (trunksOf), and fall back to main, said, only when it
names none. A force-push onto any trunk is refused, and trunk_rule says
whether the branch asked is a trunk.

modules/gitea/module.json

@@ -569,6 +569,7 @@
     "mesh-build-node.keys",
     "mesh-build-image.keys",
     "mesh-delivery-checker.owed",
-    "mesh-delivery-indexer.modules"
+    "mesh-delivery-indexer.modules",
+    "mesh-delivery-gate.source"
   ]
 }