fix: add missing ActivityLog component to fix build

docs/project-structure.txt

@@ -125,6 +125,7 @@ Mana-Loop/
 │   │   │   │   │   ├── golemancy-utils.ts
 │   │   │   │   │   └── types.ts
 │   │   │   │   ├── AchievementsTab.tsx
+│   │   │   │   ├── ActivityLog.tsx
 │   │   │   │   ├── AttunementsTab.test.ts
 │   │   │   │   ├── AttunementsTab.tsx
 │   │   │   │   ├── CraftingTab.test.ts

src/components/game/tabs/ActivityLog.tsx

@@ -0,0 +1,40 @@
+'use client';
+
+import type { ActivityLogEntry } from '@/lib/game/types';
+import { ScrollArea } from '@/components/ui/scroll-area';
+import { DebugName } from '@/components/game/debug/debug-context';
+
+interface ActivityLogProps {
+  activityLog: ActivityLogEntry[];
+  maxEntries?: number;
+}
+
+export function ActivityLog({ activityLog, maxEntries = 30 }: ActivityLogProps) {
+  const entries = activityLog.slice(0, maxEntries);
+
+  return (
+    <DebugName name="ActivityLog">
+      <ScrollArea className="h-48">
+        {entries.length === 0 ? (
+          <div className="text-xs text-gray-500 italic">No activity yet.</div>
+        ) : (
+          <div className="space-y-1">
+            {entries.map((entry) => (
+              <div
+                key={entry.id}
+                className="text-xs text-gray-300 border-b border-gray-800 pb-1 last:border-0"
+              >
+                <span className="text-gray-600 mr-1">
+                  [{entry.eventType}]
+                </span>
+                {entry.message}
+              </div>
+            ))}
+          </div>
+        )}
+      </ScrollArea>
+    </DebugName>
+  );
+}
+
+ActivityLog.displayName = 'ActivityLog';