Implement upsert label flow and use-based mark gone handling

AGENTS.md

@@ -82,16 +82,19 @@ These are current project assumptions and should not be casually changed.
 - `/{database}/user/application/`
 - `/{database}/kitchen/kitchens`
 - `/{database}/kitchen/items`
+- `/{database}/kitchen/items/upsert`
 - `/{database}/kitchen/items/grouped`
 - `/{database}/kitchen/items/{uuid_b64}`
 - `/{database}/kitchen/items/{uuid_b64}/stock`
+- `/{database}/kitchen/items/{uuid_b64}/use`
+- `/{database}/kitchen/changes`
 - `/{database}/kitchen/locations`
 
 ### Labels
 
 - Preview uses label-preview flags
-- Create uses label-generation flags
-- Actual create currently also needs `print=1`
+- Submit/create flow uses upsert apply (`/kitchen/items/upsert?mode=apply`)
+- Auto-print is deferred and should not be assumed in current UI submit flow
 
 ### Item-definition search for label creation