Remove Cell::shared1 and Cell::shared2, use tempValue1/tempValue2 instead

[Copilot]

Consolidate shared1/shared2 fields into the existing TempValue union fields. These serve the same role (per-object scratch storage across kernel phases) and never overlap temporally — physics uses them for force accumulation, then cell state transitions reuse the same memory via the as_uint32_float view.

• Remove float2 shared1 and float2 shared2 from Object struct in Entities.cuh
• Replace all usages in ObjectProcessor.cuh: shared1 → tempValue1.as_float2, shared2 → tempValue2.as_float2
• Drop redundant shared1 = {0,0} init (already covered by tempValue1.as_uint64 = 0)

// Before
object->shared1 += F_pressure * strength * density;
atomicAdd(&otherObject->shared1.x, force.x);
object->shared2 = object->shared1;  // forces

// After
object->tempValue1.as_float2 += F_pressure * strength * density;
atomicAdd(&otherObject->tempValue1.as_float2.x, force.x);
object->tempValue2.as_float2 = object->tempValue1.as_float2;

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