Houdini22 usd26 sdr port

[gripeyes]

Compatibility:

minor

Issues/Tickets:

OpenMoonRay/openmoonray#276
#5

Release notes comment:

Ported MoonRay shader discovery and parser plugins to the USD 26.05 Sdr APIs.

Comments for the reviewer:

This PR is stacked on #5 because both changes touch the shader-plugin module registration. Once #5 merges, this PR will contain only the USD 26.05 port.

The port:

• replaces removed Ndr discovery and parser interfaces with their Sdr equivalents
• updates plugin registration and metadata to use Sdr
• removes the obsolete Ndr library dependency
• updates shader node, property, token-map and option types
• links Houdini’s wrapped PXR-Python library on macOS where required

Unrelated whitespace changes from the original validation commit were removed.

Umbrella validation PR:
OpenMoonRay/openmoonray#276

Houdini 22 build notes:
https://github.com/gripeyes/openmoonray/blob/test/houdini22-clean-build/building/macOS/Houdini22_build_notes.md

Look or scene setup change:

No expected look change.

Special notes for production:

Requires USD 26 Sdr plugin APIs.

Attention/Reviewers:

AI Assisted Development:

Assisted-by: OpenAI Codex / GPT-5.6

Checklist:

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

[gripeyes]

ndr is deprecated now, replaced by sdr:
https://forum.aousd.org/t/deprecation-of-pxr-usd-ndr/2167/2