UX: surface swap-back item on magic-item equip

resolveMagicEquipReply silently sold the previously equipped curio back
to inventory at full value, but the success DM only named the new item.
Players had to !sheet or !inv to confirm the old one wasn't lost.

Capture the prior occupant's name before the delete and append a
"📦 **<name>** moved back to inventory." line to the equip confirmation
when a swap actually happened.

internal/plugin/magic_items_gameplay.go

@@ -526,12 +526,14 @@ func (p *AdventurePlugin) resolveMagicEquipReply(ctx MessageContext, interaction
 	// value — swapping a curio shouldn't tax it. Evict from the local map
 	// too, so the attunement count below reflects the post-swap state and
 	// can re-open a slot the prior occupant was holding.
+	var swappedBackName string
 	if prev, exists := equipped[mi.Slot]; exists && prev.Item.ID != "" {
 		back := magicItemSell(prev.Item)
 		back.SkillSource = "magic_item:" + prev.Item.ID
 		if err := addAdvInventoryItem(ctx.Sender, back); err != nil {
 			return p.SendDM(ctx.Sender, "Failed to return your currently-equipped item to inventory.")
 		}
+		swappedBackName = prev.Item.Name
 		delete(equipped, mi.Slot)
 	}
 
@@ -571,6 +573,9 @@ func (p *AdventurePlugin) resolveMagicEquipReply(ctx MessageContext, interaction
 	var sb strings.Builder
 	sb.WriteString(fmt.Sprintf("✨ **%s** equipped in your %s slot — %s.",
 		mi.Name, mi.Slot, magicItemEffectSummary(mi)))
+	if swappedBackName != "" {
+		sb.WriteString(fmt.Sprintf("\n📦 **%s** moved back to inventory.", swappedBackName))
+	}
 	switch {
 	case mi.Attunement && attune:
 		sb.WriteString(fmt.Sprintf("\nBonded (%d/%d bond slots used).",