Persist project locations

docs/project-history-and-external-model-architecture.md

@@ -270,11 +270,18 @@ Completed foundation:
   list and default-section structure with stable ids; its delete inverse
   refuses changed or populated structures and the project-page POST tracks the
   returned revision
+- `project-floor.insert` and `project-room.insert` persist complete location
+  records with stable ids; their inverses reject changed or referenced records
+  so Undo never clears room assignments or device-row links implicitly
+- the floor and room POST routes require the current expected revision and the
+  project page tracks the returned history state
 
 Remaining constraints before completing project version history:
 
-- extend project-scoped commands only when further project mutations are
-  deliberately added to history; the generic versioned envelope is complete
+- all current normal project-scoped runtime writes are behind the revision
+  boundary; extend it whenever further project mutations are introduced
+- project creation remains initialization at revision zero, while global device
+  templates remain outside any single project history
 - do not model IFCGUID as an overloaded circuit equipment identifier
 - keep database backup/restore checks separate from project history tests