ci: add grog wheel install smoke tests

[GeorgePearse]

Summary

• Add a Grog build graph (BUILD.yaml + grog.toml) that builds wheels and smoke-tests uv pip install from the produced wheel.
• Add a small optional demo C-extension build via a Hatchling build hook (enabled only with VISDET_BUILD_CPP_EXT=1) to validate compiled extension packaging.
• Fix wheel packaging to force-include visdet/engine/dist/** (Hatchling otherwise drops it due to the dist directory name), ensuring uv pip install visdet remains importable.

How to run locally

• grog test

[github-actions]

🤖 Multi-Model Consensus Review

Model	Status
Claude Sonnet 4	✅
GPT-4o	✅
Gemini 2.0 Flash	✅

✅ hatch_build.py

Pass Rate: 3/3 models

✅ visdet/_ext_demo/__init__.py

Pass Rate: 3/3 models

[github-actions]

✅ Skylos Scan: No dead code or security issues detected.