docs: set up staging and docs.nvidia.com publishing pipeline

[miyoungc]

Description

Configure the staging preview and production publishing pipeline so NemoClaw documentation is published to docs.nvidia.com, following the same pattern used by NeMo RL https://github.com/NVIDIA-NeMo/RL.

Scope

• Register the NemoClaw docset with the sw-gpu-doctools/docs-ci GitLab CI project
• Create a project-specific CI config (e.g. nemoclaw/docs-ci.yaml) in the doctools repo
• Add the GitLab CI include to .gitlab-ci.yml for the docs stage
• Set up staging URL for pre-release doc review (e.g. docs-staging.nvidia.com/nemo/nemoclaw/...)
• Verify end-to-end: merge to main → staging build → production publish at docs.nvidia.com/nemo/nemoclaw/latest/
• Configure version switcher data (versions1.json) and html_baseurl in conf.py
• Set up project.json with docset name and version

Dependencies

• Initial docs/ infrastructure must be in place (see related issue)

Definition of Done

• Merges to main trigger a staging build visible at the staging URL
• Tagged releases publish to docs.nvidia.com
• Version switcher shows available versions

[miyoungc]

NVIDIA/NemoClaw#160