feat: 新增 Physical_Only 预处理分支 — 纯物理特征+标准化，与 MNF A/B 对比

spectral_Preprocessing.py:
- 新增 Physical_Only 分支: Pipeline[PhysicalFeatureExtractor + StandardScaler]
- 纯物理特征流: 20个指数 → StandardScaler → SVR
- DualStream_MNF 逻辑完全不变

modeling_batch.py:
- preprocessing_methods 新增 Physical_Only
- 训练时 Physical_Only 也只取纯光谱50列
- 波长列表传递覆盖 Physical_Only

GUI:
- 两个面板同步新增「纯物理特征 (指数+标准化)」选项

src/core/modeling/modeling_batch.py

@@ -241,7 +241,7 @@ class WaterQualityModelingBatch:
         # 预处理方法列表
         self.preprocessing_methods = [
             "None", "MMS", "SS", "CT", "SNV", "MA", "SG", "MSC", "D1", "D2", "DT", "WVAE",
-            "DualStream_MNF"
+            "DualStream_MNF", "Physical_Only"
         ]
 
         # 样本划分方法列表
@@ -609,10 +609,10 @@ class WaterQualityModelingBatch:
         # ═══════════════════════════════════════════════════════════
         # ★ DualStream_MNF：只取纯光谱列，WQI 由 Pipeline 内 PhysicalExtractor 动态计算
         # ═══════════════════════════════════════════════════════════
-        if preprocess_method == "DualStream_MNF":
+        if preprocess_method in ("DualStream_MNF", "Physical_Only"):
             _spec_cols = [c for c in X_raw.columns if self._is_wavelength_column(c)]
             X_raw = X_raw[_spec_cols]
-            print(f"[DualStream_MNF] 精简为纯光谱: {X_raw.shape[1]} 列 "
+            print(f"[{preprocess_method}] 精简为纯光谱: {X_raw.shape[1]} 列 "
                   f"({X_raw.columns[0]} ~ {X_raw.columns[-1]} nm)")
 
         # 使用指定方法分割训练集和测试集
@@ -637,9 +637,9 @@ class WaterQualityModelingBatch:
             base_model.set_params(verbose=-1)
 
         # ============ 关键：把预处理器塞进 Pipeline ============
-        # DualStream_MNF 需要传入波长列表，供 PhysicalFeatureExtractor 定位波段
+        # DualStream_MNF / Physical_Only 需要波长列表，供 PhysicalFeatureExtractor 定位波段
         _wl_list = None
-        if preprocess_method == "DualStream_MNF":
+        if preprocess_method in ("DualStream_MNF", "Physical_Only"):
             _wl_list = self._extract_train_wavelengths(X_raw.columns)
         preproc = get_preprocessing_transformer(preprocess_method, wavelengths=_wl_list)
         pipeline = Pipeline([