fix(ai500): flat API response for the panel, list-format chat replies

- /api/ai500 returned a success/data envelope but the web httpClient
  wraps the raw body as data, so the panel read coins as undefined and
  showed the empty state; return a flat {coins,count} body like
  /api/symbols
- the agent rendered AI500 rankings as a markdown table that the chat
  UI flattens into an unreadable line: tool note + system prompt now
  mandate numbered lists (one coin per line) and ban tables outright

api/handler_ai500.go

@@ -33,11 +33,11 @@ func (s *Server) handleAI500List(c *gin.Context) {
 		return
 	}
 
+	// Flat body, matching /api/symbols: the web httpClient wraps the raw
+	// response body as `data`, so a nested success/data envelope here would
+	// hide the coins from the panel.
 	c.JSON(http.StatusOK, gin.H{
-		"success": true,
-		"data": gin.H{
-			"coins": entries,
-			"count": len(entries),
-		},
+		"coins": entries,
+		"count": len(entries),
 	})
 }