refactor: 移除主界面重复代码，复用现有组件并彻底抽离图像控件

src/gui/core/viz_thread.py

@@ -13,6 +13,11 @@ from PyQt5.QtCore import QThread, pyqtSignal
 import numpy as np
 
 
+def _viz_training_spectra_csv_path(work_path: Path) -> Path:
+    """可视化光谱/统计及模型散点图使用的训练光谱表路径（与步骤5输出一致）。"""
+    return work_path / "5_training_spectra" / "training_spectra.csv"
+
+
 def _viz_infer_wavelength_start_column(df) -> Union[str, int]:
     """推断光谱起始列（training_spectra 通常以波长数值为列名，未必含 UTM_Y）。"""
     import pandas as pd