Fix: background splitting bug

docs/RELEASE_TESTING.md

@@ -134,6 +134,14 @@ Bevy window-management verification workflow: `docs/BEVY_WINDOW_VERIFICATION.md`
 - run repeated character switch cycles (`default` <-> `ferris`) and move scale slider each cycle
 - ensure no runtime frontend exception is shown (debug overlay/console)
 - ensure no visible magenta fringe remains around sprite edges after chroma-key conversion
+12. Verify packaged tauri scale anchoring and bounds:
+- repeated scale changes resize around window center (no consistent bottom-right drift)
+- window remains visible on the current monitor (no off-screen drift)
+- no runtime scale-path exception appears (for example monitor lookup API errors)
+ - no runtime position-arg exceptions appear during scale (e.g. float passed to integer position API)
+ - at large scale values (>= 1.8), full sprite remains visible without clipping
+13. Verify packaged tauri frontend freshness:
+- confirm package run reflects latest `frontend/tauri-ui` changes (no stale embedded UI bundle)
 
 ### Packaged Mode (Required Once Tauri Packaging Exists)
 

docs/TAURI_RUNTIME_TESTING.md

@@ -114,6 +114,13 @@ An issue touching Tauri runtime behaviors must satisfy all requirements before `
 - scaling behavior remains responsive after each pack switch
 8. Chroma-key quality check:
 - verify no visible magenta (`#FF00FF`) fringe remains around sprite edges in normal runtime view
+9. Scale anchor and bounds check:
+- repeated scale changes should keep window centered without directional drift
+- window must remain within current monitor bounds during scale adjustments
+- no runtime error is allowed from monitor lookup during scale operations (e.g. `currentMonitor`
+  API mismatch)
+- verify window resize uses consistent coordinate units (no accumulated drift over 20 scale changes)
+- no runtime command/type error from position updates (e.g. `set_position` expects integer coords)
 
 ## Settings Window Checklist