feat(skills): add Kangaroo model inbox

[BramVR]

Summary

• add the reusable Kangaroo Maya 2022 model-inbox skill
• standardize canonical dark HTML report lookup and complete per-check summaries
• preserve source-model safety and isolate checks from unrelated Maya sessions

Validation

• quick_validate.py skills/kangaroo-model-inbox — passed
• staged diff check — passed
• autoreview — clean, no actionable findings

Related implementation

• GitLab gg_kangaroo_buildscripts MR !3 contains the Maya 2022 inbox worker and HTML report implementation.
• The newest exact-head Maya 2022 rerun remains blocked by the dedicated host lease, so this PR is intentionally draft.