Fix 16-bit export bugs and UI inconsistencies

[google-labs-jules]

This submission addresses critical bugs in the Material Baker plugin.

1. 16-bit Export Fix: The export pipeline for PNG and TGA formats previously wrote raw Float16 data to files expected to be UNORM16. This resulted in corrupted/unreadable images. The fix implements a proper conversion step that quantizes linear floating-point data to 16-bit integers (0-65535). It also includes a high-precision sRGB conversion path (using pow(x, 1/2.2)) to ensure 16-bit data is not crushed to 8-bit precision before saving.
2. UI Logic Correction: The logic for enabling/disabling bit depth options (e.g., forcing 8-bit for JPEG) was previously only triggered when changing Compression Settings, not Output Type. This logic has been centralized in UpdateUIToReflectOutputType and hooked up correctly. Additionally, the code now explicitly updates the visible selection of the SComboBox to match the internal state, preventing misleading UI states.
3. Configuration Alignment: Added the missing JPEG output option and removed the Normal property to strictly adhere to the "Minimum Configuration" requirements specified in the documentation/memory.
4. Tests: Added MaterialBakerTests.cpp to verify constant availability and export logic correctness (compile-only verification in this env).

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PR created automatically by Jules for task 14730134697541194837 started by @EmbarrassingMoment

[google-labs-jules]

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