Implement proper scene cloning

[waynemwashuma]

Objective

• Introduce type-safe cloning of via TypeRegistry
• Fix incorrect static polymorphism in clone() implementations
• Implement cloning semantics into the scene system

Solution

1. Incorrect this.copy usage in static context

Using this.copy() inside static methods is unsafe under inheritance. It may resolve to the wrong constructor or break when methods are detached and no context binding for this.

Fix:

• Replaced all:

  static clone(target) {
    return this.copy(target)
  }

  with:

  static clone(target) {
    return ClassName.copy(target)
  }

Why:
Ensures deterministic dispatch and avoids reliance on dynamic this binding in static context.

2. Centralized cloning via TypeRegistry

Problem:
Scene instantiation previously reused component references (no cloning), leading to:

• Shared mutable state
• Broken scene isolation
• Undefined behavior in instancing

Changes:

• Resolve clone methods via TypeRegistry
• Clone each component explicitly
• Log warnings for non-cloneable components

Additional behavior:

• Automatically injects Parent if missing → guarantees hierarchy integrity.

Why this approach:

• Avoids hardcoding clone semantics per component

Showcase

• New demos:

  • multiple_instances (2D & 3D)

    • Demonstrates:
      • Scene instancing
      • Scene instance isolation from other instances

Migration guide

scene.toWorld(world, instance)

Now requires:

scene.toWorld(world, instance, typeRegistry, instanceEntity)

Custom components

If you want your component to be scene-compatible:

• Ensure it is registered in TypeRegistry
• Provide:

static copy(source, target) {}
static clone(target) {}

Notes

• Components without registered clone will be skipped with a warning
• Parent linkage is now enforced automatically during instancing

Checklist

• I have updated the documentation accordingly.
• I have added tests to cover my changes.