Expose global bone transforms to Lua

[Gopmyc]

Description

Adds read-only access to the accumulated pose of a skinned mesh bone through CSkinnedMeshRenderer and Lua:

• GetBoneGlobalPosition
• GetBoneGlobalRotation
• GetBoneGlobalScale

The getters resolve a bone index to its skeleton node and decompose the matrix already computed in m_globalPose. Invalid indices return std::nullopt in C++ and nil in Lua, consistently with the existing local bone getters.

Related Issue(s)

Fixes #831

Review Guidance

Please focus on:

• the distinction between local, skeleton-global/model-space, and world-space transforms;
• consistency with the existing GetBoneLocalPosition, GetBoneLocalRotation, and GetBoneLocalScale API;
• invalid bone-index handling in both C++ and Lua;
• the Lua API names and annotations.

The getters read m_globalPose before applying the bone offset matrix, which makes the returned transforms suitable for runtime bone attachments.

Screenshots/GIFs

1.mp4

AI Usage Disclosure

N/A

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]

Didn't test but the code looks good!