feature: Document consistent use of pattern helpers across codebase

- Add documentation to usePatternRotationUpload about using same helpers as store
- Add documentation to App.tsx pattern resume logic
- Mark PatternLayer to continue using local memoization (receives props)
- All tests passing

Co-authored-by: jhbruhn <1036566+jhbruhn@users.noreply.github.com>

src/App.tsx

@@ -112,8 +112,9 @@ function App() {
       // Use cached uploadedPesData if available, otherwise recalculate
       if (cachedUploadedPesData) {
         // Use the exact uploaded data from cache
-        // Calculate the adjusted offset (same logic as upload)
+        // Calculate the adjusted offset (same logic as upload hook)
         if (rotation !== 0) {
+          // Calculate center shift using the same helper as store selectors
           const originalCenter = calculatePatternCenter(originalPesData.bounds);
           const rotatedCenter = calculatePatternCenter(
             cachedUploadedPesData.bounds,
@@ -140,6 +141,7 @@ function App() {
         }
       } else if (rotation !== 0) {
         // Fallback: recalculate if no cached uploaded data (shouldn't happen for new uploads)
+        // This uses the same transformation logic as usePatternRotationUpload hook
         console.warn("[App] No cached uploaded data, recalculating rotation");
         const rotatedStitches = transformStitchesRotation(
           originalPesData.stitches,
@@ -152,6 +154,7 @@ function App() {
         const decoded = decodePenData(penData);
         const rotatedBounds = calculateBoundsFromDecodedStitches(decoded);
 
+        // Calculate center shift using the same helper as store selectors
         const originalCenter = calculatePatternCenter(originalPesData.bounds);
         const rotatedCenter = calculatePatternCenter(rotatedBounds);
         const centerShiftX = rotatedCenter.x - originalCenter.x;

src/hooks/domain/usePatternRotationUpload.ts

@@ -42,6 +42,10 @@ export interface UsePatternRotationUploadReturn {
  * - Center shift calculation to maintain visual position
  * - Upload orchestration with proper caching
  *
+ * Note: This hook operates on passed parameters rather than store state,
+ * allowing it to be used as a callback handler. The center calculations
+ * use the same helpers as the store selectors for consistency.
+ *
  * @param params - Upload and store functions
  * @returns Upload handler function
  */
@@ -78,7 +82,8 @@ export function usePatternRotationUpload({
         // Calculate bounds from the DECODED stitches (the actual data that will be rendered)
         const rotatedBounds = calculateBoundsFromDecodedStitches(decoded);
 
-        // Calculate the center of the rotated pattern
+        // Calculate the center shift caused by rotation
+        // Uses the same calculatePatternCenter helper as store selectors
         const originalCenter = calculatePatternCenter(pesData.bounds);
         const rotatedCenter = calculatePatternCenter(rotatedBounds);
         const centerShiftX = rotatedCenter.x - originalCenter.x;