Clarify remaining life export column

app/prediction.py

@@ -56,6 +56,7 @@ FEATURES = [
 
 ID_COLUMN = "管道编号"
 PIPE_AGE_COLUMN = "管龄（年）"
+REMAINING_LIFE_COLUMN = "预计剩余寿命（年）（管道健康状态 ≥0.5 的剩余年数）"
 LEGACY_PIPE_AGE_COLUMN = "管龄"
 COLUMN_ALIASES = {
     "ID": ID_COLUMN,
@@ -499,7 +500,7 @@ def render_survival_chart(predictions: list[dict[str, Any]], image_path: Path) -
                 PIPE_AGE_COLUMN: pipe_age,
                 "当前健康状态": current_health_state,
                 "健康等级": grade_label,
-                "预计剩余寿命（年）": format_years(remaining_life, current_age, max_age),
+                REMAINING_LIFE_COLUMN: format_years(remaining_life, current_age, max_age),
             }
         )
         if i < CHART_DISPLAY_LIMIT:
@@ -548,7 +549,7 @@ def write_prediction_workbook(
     with pd.ExcelWriter(excel_path, engine="openpyxl") as writer:
         summary_df = pd.DataFrame(
             summary_sheet_rows,
-            columns=[ID_COLUMN, PIPE_AGE_COLUMN, "当前健康状态", "健康等级", "预计剩余寿命（年）"],
+            columns=[ID_COLUMN, PIPE_AGE_COLUMN, "当前健康状态", "健康等级", REMAINING_LIFE_COLUMN],
         )
         sample_df = pd.DataFrame(sample_data_rows, columns=sample_columns)
         if ID_COLUMN in summary_df.columns: