Fix/houdini22 usd26 materialx hdas

[gripeyes]

Compatibility:

patch

Issues/Tickets:

OpenMoonRay/openmoonray#276
#5

Release notes comment:

Updated Houdini HDA generation for MaterialX shaders with USD 26.

Comments for the reviewer:

This PR is stacked on Nick’s #5 update.

The HDA generator now:

• Supports USD 26’s GetShaderOutputNames() and updated SDF type API.
• Retains compatibility with the older USD shader-output API.
• Handles RGBA and vector4 parameters.
• Handles matrix3 and matrix4 parameters, including nested matrix defaults.
• Parses versioned MoonRay class names more safely.

This is limited to scripts/update_hdas.py; generated HDAs are submitted separately.

Look or scene setup change:

No expected look changes.

Special notes for production:

Depends on #5.

Attention/Reviewers:

@nshelton-dwa

AI Assisted Development:

Assisted-by: OpenAI Codex / GPT-5.6

Checklist:

• Documentation has been updated.
• Includes new unit tests.
• Includes new RATS tests.

[gripeyes]

I've got a take on color management here & how it's handled w/ mtlx image in Hou, I'd like to fix it & also implement the whole color management into moonray to get as far away from how Hou handles it as possible. It's possible, I've done it on my h20.5 massive PR. A matter of discussion tho. Maybe a dedicated Moonray materailx subnetwork might work?

(I'm a bit opinionated & view this part as Hou tech debt, might be related to mtlx, but after checking the source it'd be work correctly, Hou doesn't even expose all the usd defined colorspaces https://openusd.org/dev/user_guides/color_user_guide.html )

Again, it's more on the experimental side of thigns from my side, but I got it working well w/ the native nodes. It's been a rabbit hole I had to unwillingly dig into for a couple of months. I've also built a tool to bypass sidefx colormanagement already & tweaked it for moonray's native material subnet w/ my own color management implementation. Will share it later on.