fix: address PR review comments

- Fix branch fallback logic: use nullish coalescing (??) instead of || to handle empty strings correctly (empty string represents unassigned features, not main branch)
- Refactor branchCardCounts calculation: use reduce instead of forEach for better conciseness and readability
- Fix badge semantics in BranchAutocomplete: check branchCardCounts !== undefined first to ensure numeric badges (including 0) only appear when actual count data exists, while 'default' is reserved for when count data is unavailable

apps/app/src/components/ui/branch-autocomplete.tsx

@@ -33,8 +33,8 @@ export function BranchAutocomplete({
     return Array.from(branchSet).map((branch) => {
       const cardCount = branchCardCounts?.[branch];
       // Show card count if available, otherwise show "default" for main branch only
-      const badge = cardCount !== undefined 
-        ? String(cardCount) 
+      const badge = branchCardCounts !== undefined
+        ? String(cardCount ?? 0)
         : branch === "main" 
           ? "default" 
           : undefined;

apps/app/src/components/views/board-view.tsx

@@ -272,17 +272,13 @@ export function BoardView() {
 
   // Calculate unarchived card counts per branch
   const branchCardCounts = useMemo(() => {
-    const counts: Record<string, number> = {};
-    
-    // Count unarchived features (status !== "completed") per branch
-    hookFeatures.forEach((feature) => {
+    return hookFeatures.reduce((counts, feature) => {
       if (feature.status !== "completed") {
-        const branch = feature.branchName || "main";
+        const branch = feature.branchName ?? "main";
         counts[branch] = (counts[branch] || 0) + 1;
       }
-    });
-    
-    return counts;
+      return counts;
+    }, {} as Record<string, number>);
   }, [hookFeatures]);
 
   // Custom collision detection that prioritizes columns over cards