fix: Calculate time correctly per color block using Brother formula

Implemented proper time calculation matching the Brother app algorithm:
- 150ms per stitch + 3000ms startup time per color block
- Calculate total and elapsed time by summing across color blocks
- This fixes the "999 seconds" issue by calculating time accurately

Created timeCalculation utility with:
- convertStitchesToMinutes: Convert stitches to minutes using PP1 formula
- calculatePatternTime: Calculate total/elapsed time per color blocks

Updated ProgressMonitor to show:
- Total Time (calculated from all color blocks)
- Elapsed Time / Total Time (based on current stitch position)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/components/ProgressMonitor.tsx

@@ -21,6 +21,7 @@ import {
   canResumeSewing,
   getStateVisualInfo,
 } from "../utils/machineStateHelpers";
+import { calculatePatternTime } from "../utils/timeCalculation";
 
 export function ProgressMonitor() {
   // Machine store
@@ -109,6 +110,15 @@ export function ProgressMonitor() {
       currentStitch >= block.startStitch && currentStitch < block.endStitch,
   );
 
+  // Calculate time based on color blocks (matches Brother app calculation)
+  const { totalMinutes, elapsedMinutes } = useMemo(() => {
+    if (colorBlocks.length === 0) {
+      return { totalMinutes: 0, elapsedMinutes: 0 };
+    }
+    const result = calculatePatternTime(colorBlocks, currentStitch);
+    return { totalMinutes: result.totalMinutes, elapsedMinutes: result.elapsedMinutes };
+  }, [colorBlocks, currentStitch]);
+
   // Auto-scroll to current block
   useEffect(() => {
     if (currentBlockRef.current) {
@@ -185,11 +195,10 @@ export function ProgressMonitor() {
           </div>
           <div className="bg-gray-50 dark:bg-gray-700/50 p-2 rounded">
             <span className="text-gray-600 dark:text-gray-400 block">
-              Est. Time
+              Total Time
             </span>
             <span className="font-semibold text-gray-900 dark:text-gray-100">
-              {Math.floor(patternInfo.totalTime / 60)}:
-              {String(patternInfo.totalTime % 60).padStart(2, "0")}
+              {totalMinutes} min
             </span>
           </div>
           <div className="bg-gray-50 dark:bg-gray-700/50 p-2 rounded">
@@ -225,11 +234,10 @@ export function ProgressMonitor() {
             </div>
             <div className="bg-gray-50 dark:bg-gray-700/50 p-2 rounded">
               <span className="text-gray-600 dark:text-gray-400 block">
-                Time Elapsed
+                Time
               </span>
               <span className="font-semibold text-gray-900 dark:text-gray-100">
-                {Math.floor(sewingProgress.currentTime / 60)}:
-                {String(sewingProgress.currentTime % 60).padStart(2, "0")}
+                {elapsedMinutes} / {totalMinutes} min
               </span>
             </div>
           </div>

src/utils/timeCalculation.ts

@@ -0,0 +1,67 @@
+/**
+ * Convert stitch count to minutes using Brother PP1 timing formula
+ * Formula: ((pointCount - 1) * 150 + 3000) / 60000
+ * - 150ms per stitch
+ * - 3000ms startup time
+ * - Result in minutes (rounded up)
+ */
+export function convertStitchesToMinutes(stitchCount: number): number {
+  if (stitchCount <= 1) return 0;
+
+  const timeMs = (stitchCount - 1) * 150 + 3000;
+  const timeMin = Math.ceil(timeMs / 60000);
+
+  return timeMin < 1 ? 1 : timeMin;
+}
+
+/**
+ * Calculate total and elapsed time for a pattern based on color blocks
+ * This matches the Brother app's calculation method
+ */
+export function calculatePatternTime(
+  colorBlocks: Array<{ stitchCount: number }>,
+  currentStitch: number
+): {
+  totalMinutes: number;
+  elapsedMinutes: number;
+  remainingMinutes: number;
+} {
+  let totalMinutes = 0;
+  let elapsedMinutes = 0;
+  let cumulativeStitches = 0;
+
+  // Calculate time per color block
+  for (const block of colorBlocks) {
+    totalMinutes += convertStitchesToMinutes(block.stitchCount);
+    cumulativeStitches += block.stitchCount;
+
+    if (cumulativeStitches < currentStitch) {
+      // This entire block is completed
+      elapsedMinutes += convertStitchesToMinutes(block.stitchCount);
+    } else if (cumulativeStitches === currentStitch) {
+      // We just completed this block
+      elapsedMinutes += convertStitchesToMinutes(block.stitchCount);
+      break;
+    } else {
+      // We're partway through this block
+      const stitchesInBlock = currentStitch - (cumulativeStitches - block.stitchCount);
+      elapsedMinutes += convertStitchesToMinutes(stitchesInBlock);
+      break;
+    }
+  }
+
+  return {
+    totalMinutes,
+    elapsedMinutes,
+    remainingMinutes: Math.max(0, totalMinutes - elapsedMinutes),
+  };
+}
+
+/**
+ * Format minutes as MM:SS
+ */
+export function formatMinutes(minutes: number): string {
+  const mins = Math.floor(minutes);
+  const secs = Math.round((minutes - mins) * 60);
+  return `${mins}:${String(secs).padStart(2, '0')}`;
+}