docs: Update documentation to use V1 environment variables

[neubig]

Summary of PR

This PR updates all documentation to use the new V1 environment variables (AGENT_SERVER_IMAGE_REPOSITORY and AGENT_SERVER_IMAGE_TAG) instead of the deprecated SANDBOX_RUNTIME_CONTAINER_IMAGE.

Root Cause of OpenHands/OpenHands#12495:
The V1 code expects AGENT_SERVER_IMAGE_REPOSITORY and AGENT_SERVER_IMAGE_TAG environment variables, but the documentation was still using the old SANDBOX_RUNTIME_CONTAINER_IMAGE variable. This caused users following the documentation to get "Sandbox failed to start within 120s" errors.

Files Updated:

• openhands/usage/run-openhands/local-setup.mdx - Main Docker setup instructions
• openhands/usage/cli/installation.mdx - CLI installation instructions
• openhands/usage/runtimes/docker.mdx - Docker runtime documentation
• openhands/usage/troubleshooting/troubleshooting.mdx - Troubleshooting examples
• openhands/usage/environment-variables.mdx - Environment variables reference
• openhands/usage/llms/local-llms.mdx - Local LLM setup instructions
• openhands/usage/advanced/custom-sandbox-guide.mdx - Custom sandbox guide

Companion PR: OpenHands/OpenHands#12522 (updates docker-compose files in main repo)

Fixes

Fixes OpenHands/OpenHands#12495

@neubig can click here to continue refining the PR

[openhands-ai]

Looks like there are a few issues preventing this PR from being merged!

• GitHub Actions are failing:
  • .github/workflows/sync-docs-code-blocks.yml
  • .github/workflows/sync-agent-sdk-openapi.yml

If you'd like me to help, just leave a comment, like

@OpenHands please fix the failing actions on PR #269 at branch `openhands/update-docs-env-vars`

Feel free to include any additional details that might help me get this PR into a better state.

_{^{You can manage your notification settings}}

[neubig]

I have confirmed that these new instructions work:

$ docker run -it --rm --pull=always     -e AGENT_SERVER_IMAGE_REPOSITORY=docker.openhands.dev/openhands/runtime     -e AGENT_SERVER_IMAGE_TAG=1.2-nikolaik     -e LOG_ALL_EVENTS=true     -v /var/run/docker.sock:/var/run/docker.sock     -v ~/.openhands:/.openhands     -p 3000:3000     --add-host host.docker.internal:host-gateway     --name openhands-app     docker.openhands.dev/openhands/openhands:1.2
1.2: Pulling from openhands/openhands
Digest: sha256:3ba0a4b10738b9378c2f855b25ec01cd9bc0e15e3d5c96a1e19e4341d436ca8a
Status: Image is up to date for docker.openhands.dev/openhands/openhands:1.2
Starting OpenHands...
Running OpenHands as root