Move absbc into per-iteration loop with density recomputation

[Copilot]

• Analyze current absbc call placement issue in dynamic.f90
• Remove absbc call from preparation phase (was only called once at iter=0)
• Add absbc call inside per-iteration time-stepping loop after Step 3
• Avoid double density computation: skip add_density in propagation loop when nabsorb > 0; compute densities once after absbc masks psi
• Code review - no issues found

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[aaron-philip]

Ok Copilot is right, my fault!

[kylegodbey]

@copilot We likely don't need to compute the densities twice, then. If nabsorb > 0, then don't compute the densities after the time step.

[Copilot]

@copilot We likely don't need to compute the densities twice, then. If nabsorb > 0, then don't compute the densities after the time step.

Done in commit de87ed9. The add_density call in the Step 3 propagation loop is now skipped when nabsorb > 0 (via IF(nabsorb == 0)), and similarly collect_densities is only called when nabsorb == 0. The redundant density reset inside the absbc block was also removed — densities are already zero from the Step 3 reset before the loop. So when nabsorb > 0, densities are computed exactly once after absbc masks the wavefunctions.