fix(cli): unwrap base64 GPU assignment on non-Linux shells

[patil2001]

Summary

Every non-apple overlay derives the llama-server image from ${LLAMA_SERVER_IMAGE:-...}; the apple overlay hardcoded its pin, so users who set LLAMA_SERVER_IMAGE found it silently discarded on apple-backend stacks. The apple file now honors the same override while keeping its existing arm64 pin as the default.

AI Assistance

AI-assisted comparison of overlay image sources. The author reviewed override semantics across overlays and is responsible for the final diff.

Release Lane

• Stable hotfix targeting release/2.6.x
• Mainline change targeting main
• Next-minor work targeting the next feature/minor release
• Not sure; reviewer should help classify

Stable hotfix reason:

Not targeting the stable release branch directly.

Changed Surface

• Docs only
• Tests only
• Dashboard UI
• Installer
• Core runtime
• Dashboard API
• CI workflows

Validation

• Compose file parses cleanly (yaml.safe_load) - passed.