Update examples

[waynemwashuma]

Objective

Update example applications to align with the new scheduling behavior and resource-driven APIs. This primarily demonstrates that systems can now be registered directly on the App without requiring workaround plugins for ordering, while also improving example consistency by using ECS resources/components more idiomatically.

Solution

Previously, several examples relied on temporary plugins to register startup systems because directly registered app systems executed before plugin-registered systems. This was necessary to avoid ordering conflicts with internal engine systems. With scheduling behavior improved, these workarounds are no longer required.

Several examples previously initialized resources inside startup systems. These are now initialized directly during app construction. This simplifies startup flow and better reflects intended ECS resource usage.

Duplicated viewport setup logic was removed from examples and consolidated into the shared utilities module.

Why this approach

These changes better demonstrate the intended engine architecture:

• systems should register directly without plugin ordering hacks
• resources should be initialized explicitly during app setup
• entity relationships should use ECS queries/components rather than singleton resources

The examples now reflect cleaner ECS usage patterns and serve as more accurate reference implementations.

Showcase

N/A

Migration guide

No migration required.

Checklist

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