refactor(k8s): simplify deployment to use official installer

- Use official NemoClaw installer (`curl | bash`) instead of git clone/build
- Switch to `custom` provider from PR NVIDIA#648 (supersedes dynamo-specific provider)
- Remove k8s/dev/ directory (no longer needed for testing)
- Use emptyDir volumes for portability across clusters
- Add /etc/hosts workaround for endpoint validation during onboarding
- Update README with verification steps for local inference

Tested end-to-end with Dynamo vLLM backend.

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: rwipfelnv