[Model/VLA] Support MiniCPM-RobotManip

[tc-mb]

Purpose
Add support for the MiniCPM-RobotManip 1.5B VLA model.

• Add an experimental VLA runtime, libvla
• Introduce MiniCPM-RobotManip as the first supported model
• Convert and load the action head as a standalone GGUF file
• Generate robot control sequences from final libllama hidden states
• Provide llama-vla-cli
• Add the /v1/vla/predictions server endpoint
• Add GGUF reload and numerical consistency checks