SD-M2b: mesh-broker's events on the shared events stream, 7 days

The lead's ruling of 13:0x replaces 12:5x's said-subject: mesh-broker's events follow every seat, on
mesh.seat.mesh-broker.event.<event> in the shared events stream, 7 days; the bus module keeps a longer history on a
stream of its own module. So every seat family is that stream filtered to the seat's subjects: a definition says 7
days and no cap of its own, and the reader refuses anything else.

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>.<token>.<name>, the token event unless the family names its own"
+      "description": "published on mesh.seat.<seat>.event.<name>"
     },
     "family": {
       "type": "object",
@@ -97,26 +97,8 @@
           "type": "string"
         },
         "max-age-days": {
-          "type": "integer",
-          "minimum": 1
-        },
-        "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.>"
+          "const": 7,
+          "description": "the shared events stream's age: a seat's events ride it, filtered to the seat's subjects"
         }
       }
     },