C-3: a node takes its licence token from the vault (issue 1409)

The agent module asks the seat's current which licence it holds and its key,
then the vault's get for that licence's access secret sealed to its own key:
at its start, on a binding.changed with a newer generation than it applied,
and on the vault's secret-changed for the licence it holds. The applied
binding keeps the licence's key, so the vault's event is matched by the
carried key, never one formed here.

Builds: design 39 bus-and-switch §19, §18, B7, B9, B11

Claude-Session: https://claude.ai/code/session_01NcbgfHb9d4T9nq5Q6WqdiJ

modules/claude-code/module.json

@@ -29,7 +29,9 @@
     "mesh-delivery-indexer.indexer_read_modules",
     "mesh-delivery-indexer.indexer_read_manifests",
     "mesh-delivery-assigner.assigner_read_assignments",
-    "seat:anthropic-licence-manager.bindings"
+    "seat:anthropic-licence-manager.bindings",
+    "seat:anthropic-licence-manager.current",
+    "seat:mesh-vault.get"
   ],
   "consumes": [
     "mesh-delivery-indexer.views.modules",
@@ -38,7 +40,8 @@
     "mesh-catalog.seat-definition-changed",
     "mesh-catalog.seat-definition-removed",
     "claude-licence-manager.holdings.asked",
-    "claude-licence-manager.binding.changed"
+    "claude-licence-manager.binding.changed",
+    "mesh-vault.secret-changed"
   ],
   "state": [
     "servers",