SD-M2b: mesh-broker's events on mesh.seat.mesh-broker.said.<event>

The lead's ruling of 12:5x (design 25 § 12.3): mesh-broker's events ride the bus module's own stream, 30 days,
on mesh.seat.mesh-broker.said.<event>, outside the shared events stream's mesh.seat.*.event.>, so the bus never
refuses the two as overlapping.

Claude-Session: https://claude.ai/code/session_01JG73KJNrH5EgFXMKKYSrig

format/seat-definition.schema.json

@@ -83,7 +83,7 @@
       "items": {
         "$ref": "#/$defs/message"
       },
-      "description": "published on mesh.seat.<seat>.event.<name>"
+      "description": "published on mesh.seat.<seat>.<token>.<name>, the token event unless the family names its own"
     },
     "family": {
       "type": "object",
@@ -103,6 +103,20 @@
         "max-mib": {
           "type": "integer",
           "minimum": 1
+        },
+        "token": {
+          "type": "string",
+          "pattern": "^[a-z][a-z0-9-]*$",
+          "not": {
+            "enum": [
+              "event",
+              "accept",
+              "tool",
+              "call",
+              "proof"
+            ]
+          },
+          "description": "the subject's word after the seat's name, event when absent: a family kept in a stream of its own names another, outside the shared events stream's mesh.seat.*.event.>"
         }
       }
     },