Add public building project setting

docs/spec/09-distribution-board-components-and-protection-groups.md

@@ -467,11 +467,11 @@ The supported logical project snapshot and portable JSON transfer must include:
 - circuit protection-device state
 - all new component relationships and sort positions
 
-The clean pre-release baseline uses project-state schema version `1`. It
-contains the complete supported structure above and is shared by logical
-snapshots, restore, Undo/Redo and portable JSON transfer. Payloads from earlier
-development schemas are intentionally unsupported and rejected before any
-write.
+Current project-state schema version `2` contains the complete supported
+structure above and the project building classification. It is shared by
+logical snapshots, restore, Undo/Redo and portable JSON transfer. Supported
+baseline version `1` is upgraded with the non-public default; payloads from
+before that baseline are rejected before any write.
 
 Migration `0000` creates the complete relational model on an empty database.
 New defaults apply when boards, groups or circuits are created; they never
@@ -545,7 +545,7 @@ Implemented persistence:
   one-to-one ownership boundaries
 - a trigger-maintained circuit-list registry rejects normalized BMK collisions
   across circuits and distribution-board components
-- snapshot schema version `1` includes group identity, distribution-board
+- snapshot schema version `2` includes group identity, distribution-board
   components and both one-to-one protection collections
 - capture, named and automatic snapshots, restore, Undo/Redo and portable JSON
   transfers preserve the complete new relational state