fix: 変数名の重複によるSyntaxErrorを修正

- rgbToLab関数: b → bNorm, bLab に変更
- deltaE2000関数: b1, b2 → bLab1, bLab2 に変更
- 既存の変数名との衝突を解消

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

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

Author: ayutaz

src/js/app-v3.js

@@ -546,19 +546,19 @@
         // RGB to LAB color space conversion
         rgbToLab(rgb) {
             // Normalize RGB values
-            let r = rgb[0] / 255;
-            let g = rgb[1] / 255;
-            let b = rgb[2] / 255;
+            let rNorm = rgb[0] / 255;
+            let gNorm = rgb[1] / 255;
+            let bNorm = rgb[2] / 255;
 
             // Apply gamma correction
-            r = r > 0.04045 ? Math.pow((r + 0.055) / 1.055, 2.4) : r / 12.92;
-            g = g > 0.04045 ? Math.pow((g + 0.055) / 1.055, 2.4) : g / 12.92;
-            b = b > 0.04045 ? Math.pow((b + 0.055) / 1.055, 2.4) : b / 12.92;
+            rNorm = rNorm > 0.04045 ? Math.pow((rNorm + 0.055) / 1.055, 2.4) : rNorm / 12.92;
+            gNorm = gNorm > 0.04045 ? Math.pow((gNorm + 0.055) / 1.055, 2.4) : gNorm / 12.92;
+            bNorm = bNorm > 0.04045 ? Math.pow((bNorm + 0.055) / 1.055, 2.4) : bNorm / 12.92;
 
             // Convert to XYZ (D65 illuminant)
-            let x = (r * 0.4124564 + g * 0.3575761 + b * 0.1804375) * 100;
-            let y = (r * 0.2126729 + g * 0.7151522 + b * 0.0721750) * 100;
-            let z = (r * 0.0193339 + g * 0.1191920 + b * 0.9503041) * 100;
+            let x = (rNorm * 0.4124564 + gNorm * 0.3575761 + bNorm * 0.1804375) * 100;
+            let y = (rNorm * 0.2126729 + gNorm * 0.7151522 + bNorm * 0.0721750) * 100;
+            let z = (rNorm * 0.0193339 + gNorm * 0.1191920 + bNorm * 0.9503041) * 100;
 
             // Normalize for D65 illuminant
             x = x / 95.047;
@@ -573,24 +573,24 @@
             // Calculate LAB values
             const L = 116 * y - 16;
             const a = 500 * (x - y);
-            const b = 200 * (y - z);
+            const bLab = 200 * (y - z);
 
-            return [L, a, b];
+            return [L, a, bLab];
         }
 
         // CIEDE2000 color difference formula
         deltaE2000(lab1, lab2) {
             // Simplified CIEDE2000 - for full implementation, use specialized library
             // This is a reasonable approximation for our use case
-            const [L1, a1, b1] = lab1;
-            const [L2, a2, b2] = lab2;
+            const [L1, a1, bLab1] = lab1;
+            const [L2, a2, bLab2] = lab2;
 
             const dL = L2 - L1;
             const da = a2 - a1;
-            const db = b2 - b1;
+            const db = bLab2 - bLab1;
 
-            const C1 = Math.sqrt(a1 * a1 + b1 * b1);
-            const C2 = Math.sqrt(a2 * a2 + b2 * b2);
+            const C1 = Math.sqrt(a1 * a1 + bLab1 * bLab1);
+            const C2 = Math.sqrt(a2 * a2 + bLab2 * bLab2);
             const dC = C2 - C1;
 
             const dH = Math.sqrt(Math.max(0, da * da + db * db - dC * dC));