Add: global factor controlling fps base interval

docs/TAURI_RUNTIME_TESTING.md

@@ -115,7 +115,12 @@ An issue touching Tauri runtime behaviors must satisfy all requirements before `
 8. Chroma-key quality check:
 - verify no visible magenta background/fringe remains around sprite edges in normal runtime view,
   including non-exact gradient magenta atlas backgrounds (for example `ferris`/`demogorgon`)
-9. Scale anchor and bounds check:
+9. Animation tempo check for 8-frame rows:
+- looping row animations should feel very slow/readable (1 fps profile)
+- one-shot `celebrate`/`success` should run slightly faster than loops (2 fps profile)
+- tauri renderer applies an additional global slowdown factor (`x2`) over clip fps; verify perceived
+  playback matches this expectation
+10. 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`
@@ -138,10 +143,14 @@ An issue touching Tauri runtime behaviors must satisfy all requirements before `
 - main overlay auto-fits without clipping
 - persisted/runtime scale value reflects the effective fitted scale after monitor/window bounds
 - value persists after restart
-5. Toggle `Visible` and verify:
+5. Change animation speed factor slider and verify:
+- runtime animation pace updates immediately in main overlay
+- value is clamped to `1..20`
+- value persists after restart via `frontend.tauri_animation_slowdown_factor`
+6. Toggle `Visible` and verify:
 - main overlay hide/show behavior
 - persisted value survives restart
-6. Toggle `Always on top` and verify:
+7. Toggle `Always on top` and verify:
 - main window z-order behavior updates
 - persisted value survives restart