Fix Catti reaction mouths rendering left-shifted instead of centered

Catti's dual cat-mouth (two mirrored Q-curve paths sharing a center
start point) caused extractMouthPositionFromElements to return only
the left half's coordinates. Every mouth generator then computed
cx=(100+82)/2=91 instead of the true center x=100.

The fix scans all Q-curve paths in the mouth section and computes the
full horizontal extent. For Catti: startX=82, endX=118, center=100.
Single-path mouths are unaffected (the extra-path loop simply doesn't
execute). Froggi's dual-path mouth already had symmetric bounds so its
result is unchanged.

src/blobbi/ui/lib/mouth/detection.ts

@@ -82,24 +82,45 @@ function detectMouthByMarker(svgText: string): MouthDetectionResult | null {
 
 /**
  * Extract mouth position from mouth SVG elements.
+ *
+ * When the mouth section contains multiple Q-curve paths (e.g. Catti's
+ * dual cat-mouth), computes the full horizontal extent across all paths
+ * so the detected position represents the whole mouth, not just the
+ * first half.  Single-path mouths are unaffected.
  */
 function extractMouthPositionFromElements(elements: string): MouthPosition | null {
-  const pathMatch = elements.match(/d="M\s*([\d.]+)\s+([\d.]+)\s*Q\s*([\d.]+)\s+([\d.]+)\s+([\d.]+)\s+([\d.]+)"/);
-  if (pathMatch) {
-    const strokeWidthMatch = elements.match(/stroke-width="([^"]*)"/);
-    const strokeWidth = strokeWidthMatch ? strokeWidthMatch[1] : '2.5';
-    
-    return {
-      startX: parseFloat(pathMatch[1]),
-      startY: parseFloat(pathMatch[2]),
-      controlX: parseFloat(pathMatch[3]),
-      controlY: parseFloat(pathMatch[4]),
-      endX: parseFloat(pathMatch[5]),
-      endY: parseFloat(pathMatch[6]),
-      strokeAttrs: `stroke="#1f2937" stroke-width="${strokeWidth}"`,
-    };
+  const qCurveRegex = /d="M\s*([\d.]+)\s+([\d.]+)\s*Q\s*([\d.]+)\s+([\d.]+)\s+([\d.]+)\s+([\d.]+)"/g;
+  const firstMatch = qCurveRegex.exec(elements);
+  if (!firstMatch) {
+    return null;
   }
-  return null;
+
+  const strokeWidthMatch = elements.match(/stroke-width="([^"]*)"/);
+  const strokeWidth = strokeWidthMatch ? strokeWidthMatch[1] : '2.5';
+
+  // Start from the first path's coordinates
+  let minX = Math.min(parseFloat(firstMatch[1]), parseFloat(firstMatch[5]));
+  let maxX = Math.max(parseFloat(firstMatch[1]), parseFloat(firstMatch[5]));
+  const startY = parseFloat(firstMatch[2]);
+  const controlY = parseFloat(firstMatch[4]);
+  const endY = parseFloat(firstMatch[6]);
+
+  // Widen bounds with any additional Q-curve paths in the section
+  let extra: RegExpExecArray | null;
+  while ((extra = qCurveRegex.exec(elements)) !== null) {
+    minX = Math.min(minX, parseFloat(extra[1]), parseFloat(extra[5]));
+    maxX = Math.max(maxX, parseFloat(extra[1]), parseFloat(extra[5]));
+  }
+
+  return {
+    startX: minX,
+    startY,
+    controlX: (minX + maxX) / 2,
+    controlY,
+    endX: maxX,
+    endY,
+    strokeAttrs: `stroke="#1f2937" stroke-width="${strokeWidth}"`,
+  };
 }
 
 // ─── Regex-Based Detection ────────────────────────────────────────────────────