Expose prefab instantiation to Lua

[Gopmyc]

Description

Adds Scene:InstantiatePrefab(...) to Lua with optional local transform and parent.

Related Issue(s)

Fixes #808

Review Guidance

Focus on Lua overloads, prefab path resolution, and prefab source normalization.

Screenshots/GIFs

N/A

AI Usage Disclosure

Refactored code / Debugging

Checklist

• My code follows the project's code style guidelines
• When applicable, I have commented my code, particularly in hard-to-understand areas
• When applicable, I have updated the documentation accordingly
• My changes don't generate new warnings or errors
• I have reviewed and take responsibility for all code in this PR (including any AI-assisted contributions)

[adriengivry]

Instantiate prefab should be a method in OvCore::SceneSystem::Scene, and Lua should expose it. Implementation should not live in Lua bindings.

[Gopmyc]

Instantiate prefab should be a method in OvCore::SceneSystem::Scene, and Lua should expose it. Implementation should not live in Lua bindings.

While reviewing the runtime path, I found that prefab actors spawned during play mode could receive lifecycle callbacks before deserialization was complete. I fixed this by deferring startup until the instantiated hierarchy has been fully deserialized

[adriengivry]

Build failing

[Gopmyc]

Build failing

My bad 🙇
It's fixed !