fix: C/C++/Fortran 引擎补齐 wrap_position 和 t=0 驱动力

- 三引擎均新增 wrap_position 周期边界回绕（调用在 limit_in_box 后）
- 三引擎均新增 t=0 驱动力初始调用（在预热循环前）
- 至此三引擎算法与 Python 完全一致

engines/fortran/main.f90

@@ -108,6 +108,17 @@ program dynamics_f90
     allocate(traj_vx(record_steps, n), traj_vy(record_steps, n), traj_vz(record_steps, n))
 
     ! 预热
+    ! 初始时刻 t=0 驱动力（与 Python run_simulation 一致）
+    if (driving_force /= 0 .and. n_drivers > 0) then
+        call apply_driving(n, x, y, z, vx, vy, vz, 0.0d0, 0, DT, &
+                           n_drivers, drv_atom_idx, &
+                           drv_amp_x, drv_amp_y, drv_amp_z, &
+                           drv_freq_x, drv_freq_y, drv_freq_z, &
+                           drv_phi_x, drv_phi_y, drv_phi_z, &
+                           drv_has_period, drv_period_cycles, &
+                           drv_freeze_x, drv_freeze_y, drv_freeze_z)
+    end if
+
     do s = 1, warmup_steps
         if (driving_force /= 0 .and. n_drivers > 0) then
             tw = (s * 1.0d0) * DT
@@ -512,6 +523,14 @@ subroutine limit_in_box(pos, vel, lo, hi)
     end if
 end subroutine limit_in_box
 
+! 周期边界回绕（与 Python wrap_position 一致）
+subroutine wrap_position(pos, lo, hi)
+    double precision, intent(inout) :: pos
+    double precision, intent(in) :: lo, hi
+    if (pos > hi) pos = lo
+    if (pos < lo) pos = hi
+end subroutine wrap_position
+
 ! ── 显式欧拉法 ────────────
 subroutine explicit_euler_step(n, x, y, z, vx, vy, vz, m, G, B, &
                                nb, bp, bk, br, fixed, dt, &
@@ -730,6 +749,13 @@ subroutine apply_step(method, n, x, y, z, vx, vy, vz, m, G, B, &
         call limit_in_box(z(i),  vz(i), -box_a, box_a)
     end do
 
+    ! 周期边界回绕（与 Python wrap_position 一致）
+    do i = 1, n
+        call wrap_position(x(i), -box_a, box_a)
+        call wrap_position(y(i), -box_a, box_a)
+        call wrap_position(z(i), -box_a, box_a)
+    end do
+
     ! 逐自由度固定约束（与 Python apply_fixed_constraints 一致）
     do i = 1, n
         if (fixed(i,1) /= 0) then; x(i) = pos_0(i, 1); vx(i) = 0.0d0; end if