Support adding custom model list for Claude Code with modelPicker

[anthonyivn2]

Claude Code supports the modelPicker argument which would allow the user to define a custom list of models to be made available through Claude Code. ucode today does not support this option when the user uses ucode configure + ucode setup, or when the user define a list of custom models as part of a config JSON file under custom_models argument that they then run with ucode setup.

Example settings.json:

{
  "apiKeyHelper": "...",
  "env": {
    "ANTHROPIC_BASE_URL": "..."
  },
  "modelPicker": {
    "options": [
      {
        "model": "system.ai.kimi-k3",
        "label": "Kimi K3",
        "description": "Kimi K3 via Databricks AI Gateway"
      },
      {
        "model": "system.ai.glm-5-3",
        "label": "GLM 5.3",
        "description": "GLM 5.3 via Databricks AI Gateway"
      },
      {
        "model": "system.ai.glm-5-3-flash",
        "label": "GLM 5.3 Flash",
        "description": "GLM 5.3 Flash via Databricks AI Gateway"
      },
      {
        "model": "system.ai.glm-5-2",
        "label": "GLM 5.2",
        "description": "GLM 5.2 via Databricks AI Gateway"
      }
    ]
  }
}