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.