fix: plot_wave plt.show() crash when called non-interactively

Add show=False parameter to plot_wave(); when called from dynamics.py,
pass show=False and set matplotlib Agg backend to avoid NonGuiException.
Also print full traceback on failure for easier debugging.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

plot_wave.py

@@ -167,7 +167,7 @@ def compute_energy(x, y, z, vx, vy, vz, masses, mass_arr,
     return ek_sys, us_sys, ug_sys, ugr_sys
 
 
-def plot_wave(output_dir, save_gif=False, save_mp4=False):
+def plot_wave(output_dir, save_gif=False, save_mp4=False, show=True):
     """主绘图函数：读取 display.txt 并生成波形+能量动画。
 
     Args:
@@ -360,8 +360,11 @@ def plot_wave(output_dir, save_gif=False, save_mp4=False):
         except Exception as e:
             print(f"[plot_wave] 警告: MP4 输出失败 ({e})，跳过")
 
-    # ── 最后显示动画窗口 ──
-    plt.show()
+    # ── 最后显示动画窗口（仅直接运行时）──
+    if show:
+        plt.show()
+    else:
+        plt.close(fig)
     return gif_path