fix(desktop): sidebar tab animation + memory deduplication

1. Fix sidebar tab switching: replace containerVariants (staggerChildren
   without motion children) with simple fade variants. The previous
   staggerChildren:0.05 caused the container to stay at opacity:0 when
   switching to CloneManager because non-motion children couldn't
   participate in stagger animation.

2. Fix memory deduplication: add content+agentId based dedup check
   in fallbackMemory.store(). Previously same content was stored 4x
   with different IDs. Now updates importance/accessCount instead.

desktop/src/lib/intelligence-client/fallback-memory.ts

@@ -46,6 +46,27 @@ export const fallbackMemory = {
 
   async store(entry: MemoryEntryInput): Promise<string> {
     const store = getFallbackStore();
+
+    // Content-based deduplication: update existing entry with same agentId + content
+    const normalizedContent = entry.content.trim().toLowerCase();
+    const existingIdx = store.memories.findIndex(
+      m => m.agentId === entry.agent_id && m.content.trim().toLowerCase() === normalizedContent
+    );
+
+    if (existingIdx >= 0) {
+      // Update existing entry instead of creating duplicate
+      const existing = store.memories[existingIdx];
+      store.memories[existingIdx] = {
+        ...existing,
+        importance: Math.max(existing.importance, entry.importance ?? 5),
+        lastAccessedAt: new Date().toISOString(),
+        accessCount: existing.accessCount + 1,
+        tags: [...new Set([...existing.tags, ...(entry.tags ?? [])])],
+      };
+      saveFallbackStore(store);
+      return existing.id;
+    }
+
     const id = `mem_${Date.now()}_${generateRandomString(6)}`;
     const now = new Date().toISOString();