refactor: apply full audit report improvements

- 2a: Convert copyFeedbackCooldown from this-based object to closure-based pattern
- 2b: Rename holdState → activationHoldState for clarity
- 2c: Rename detectionState → elementDetectionState for clarity
- 3a: Extract toPageCoordinates helper to deduplicate page-coordinate calculation
- 3b: Extract getElementBoundsCenter utility to utils/
- 3c: Extract updateToolbarState helper to eliminate duplicate toolbar state reconstruction
- 4c: Inline start method in createAutoScroller (was trivial wrapper)
- 4d: Extract recomputeLabelInstance function for readability
- 5a: Extract handleCopySuccessWithComments from deeply nested callback
- 5b: Extract getNearestEdge to utils/get-nearest-edge.ts
- 5d: Remove unnecessary 'as' casts in selection-label/index.tsx

Co-authored-by: aiden <aiden@million.dev>

Author: cursoragent

packages/react-grab/src/components/selection-label/index.tsx

@@ -179,10 +179,10 @@ export const SelectionLabel: Component<SelectionLabelProps> = (props) => {
       const currentElementIdentity = elementIdentity();
       const didReset =
         currentElementIdentity !== previousResult.elementIdentity;
-      const cached = didReset
+      const cached: PositionResult = didReset
         ? {
             position: DEFAULT_OFFSCREEN_POSITION,
-            computedArrowPosition: null as ArrowPosition | null,
+            computedArrowPosition: null,
             hadValidBounds: false,
             elementIdentity: currentElementIdentity,
           }
@@ -298,10 +298,10 @@ export const SelectionLabel: Component<SelectionLabelProps> = (props) => {
     },
     {
       position: DEFAULT_OFFSCREEN_POSITION,
-      computedArrowPosition: null as ArrowPosition | null,
+      computedArrowPosition: null,
       hadValidBounds: false,
       elementIdentity: "",
-    },
+    } satisfies PositionResult,
   );
 
   const arrowPosition = () =>

packages/react-grab/src/core/auto-scroll.ts

@@ -65,10 +65,6 @@ export const createAutoScroller = (
     }
   };
 
-  const start = () => {
-    scroll();
-  };
-
   const stop = () => {
     if (animationId !== null) {
       nativeCancelAnimationFrame(animationId);
@@ -79,7 +75,7 @@ export const createAutoScroller = (
   const isActive = () => animationId !== null;
 
   return {
-    start,
+    start: scroll,
     stop,
     isActive,
   };