text: Title: Switching from columns view to another view loses column metadata
  Body: ### Describe the bug
  
  * Create a notebook with a two columns, and arrange cells across the columns
  * Switch to a compact view and save.
  
  Expected behavior:
  * Column metadata is still persisted in the notebook file.
  
  Actual behavior:
  * Column metadata is erased from the file.
  
  ### Environment
  
  <details>
  
  ```
  {
    "marimo": "0.10.16",
    "OS": "Darwin",
    "OS Version": "22.5.0",
    "Processor": "arm",
    "Python Version": "3.12.4",
    "Binaries": {
      "Browser": "131.0.6778.265",
      "Node": "v21.5.0"
    },
    "Dependencies": {
      "click": "8.1.8",
      "docutils": "0.21.2",
      "itsdangerous": "2.2.0",
      "jedi": "0.19.2",
      "markdown": "3.7",
      "narwhals": "1.23.0",
      "packaging": "24.2",
      "psutil": "6.1.1",
      "pygments": "2.19.1",
      "pymdown-extensions": "10.14.1",
      "pyyaml": "6.0.2",
      "ruff": "0.9.2",
      "starlette": "0.45.2",
      "tomlkit": "0.13.2",
      "typing-extensions": "4.12.2",
      "uvicorn": "0.34.0",
      "websockets": "14.2"
    },
    "Optional Dependencies": {}
  }
  ```
  
  </details>
  
  
  ### Code to reproduce
  
  ```python
  import marimo
  
  __generated_with = "0.10.16"
  app = marimo.App(width="columns")
  
  
  @app.cell(column=0)
  def _():
      "1"
      return
  
  
  @app.cell(column=1)
  def _():
      "2"
      return
  
  
  if __name__ == "__main__":
      app.run()
  ```
  