fix: use type conversion instead of struct literal for NPCTagInfo (S1016)

Fixes staticcheck S1016: TagInfo and NPCTagInfo have identical fields,
so direct type conversion is cleaner than field-by-field struct literal.

https://claude.ai/code/session_01PeB1HsjEYNPSY2iqa7sqqR

Author: claude

internal/plugins/npcs/service.go

@@ -76,9 +76,7 @@ func (s *npcService) ListNPCs(ctx context.Context, campaignID string, role int,
 			for i := range cards {
 				if infos, ok := tagMap[cards[i].ID]; ok {
 					for _, t := range infos {
-						cards[i].Tags = append(cards[i].Tags, NPCTagInfo{
-							ID: t.ID, Name: t.Name, Slug: t.Slug, Color: t.Color,
-						})
+						cards[i].Tags = append(cards[i].Tags, NPCTagInfo(t))
 					}
 				}
 			}