Keep support arrays aligned on neighbor rebuild

[AhmedSalih3d]

Motivation

• Rebuilding neighbor/cell lists sorts SimParticles in place which can desynchronize separate per-particle work arrays (e.g. Positionₙ⁺, Velocityₙ⁺, ρₙ⁺, dρdtI, ∇Cᵢ, ∇◌rᵢ) and corrupt the integrator when ShouldRebuild is triggered frequently.
• The intent is to make the neighbor-list rebuild path safe when rebuilds occur every iteration by keeping auxiliary arrays indexed consistently with the sorted particle array.

Description

• Added UpdateNeighborsAligned! which computes the cell-sort permutation, applies it to Particles, and then applies the same permutation to any provided aligned per-particle arrays before rebuilding cell ranges (new functions in src/SPHNeighborList.jl).
• Factored the cell-range reconstruction into RebuildCellRanges! and updated UpdateNeighbors! to reuse that helper so the legacy path is preserved.
• Replaced the initial and conditional neighbor-rebuild calls in the simulation loop to use UpdateNeighborsAligned!, passing dρdtI, Velocityₙ⁺, Positionₙ⁺, ρₙ⁺, ∇Cᵢ, and ∇◌rᵢ so these support arrays stay aligned with SimParticles (src/SPHCellList.jl).
• Exported the new API symbol and added a regression test aligned neighbor rebuild to test/runtests.jl; tests were also updated to use current Δt and FullTimeStep argument forms.

Testing

• Ran the package test suite with julia --project=. -e 'using Pkg; Pkg.test()', and the full test suite passed.
• The new regression test verifies that an auxiliary array is reordered consistently with particle IDs after UpdateNeighborsAligned! and succeeded under test.

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Codex Task