Remove AccelerationMax buffer and compute max acceleration from Acceleration vector

[AhmedSalih3d]

Motivation

• Eliminate the separate per-particle AccelerationMax buffer to reduce memory allocations and duplication.
• Compute the timestep criterion from the existing per-particle acceleration vectors instead of maintaining a separate magnitude array.
• Keep neighbor-loop kernels unchanged in behavior while removing the extra write of norms during interaction accumulation.

Description

• Changed UpdateTimeStep signature to accept the Acceleration vector and replaced maximum(AccelerationMax) with a manual single-pass loop that computes norm(Acceleration[i]) using @inbounds @simd to avoid extra allocations.
• Removed the AccelerationMax parameter from all NeighborLoopPerParticle! method signatures and deleted the per-particle assignment AccelerationMax[i] = norm(acc_acc) inside those loops.
• Updated call sites in src/SPHCellList.jl to stop allocating/using AccelerationMax and to pass Acceleration into UpdateTimeStep.
• Removed the temporary allocation of AccelerationMax in the simulation initialization path so the timestep is derived directly from the Acceleration buffer.

Testing

• No automated tests were run as part of this change.

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Codex Task