Can't get titles on repeated pie charts

[mtravers]

Bug Description

I have a row of 3 pie charts, using repeat. The charts are fine but I can't get titles to display for them, no matter what I try.

{
  "data": {
    "values": [
      {"site": "CoH", "patients": "6", "samples": "11", "features": "8970"},
      {"site": "CHOP", "patients": "94", "samples": "218", "features": "8942"},
      {"site": "UCLA", "patients": "12", "samples": "20", "features": "8665"},
      {"site": "UCSF", "patients": "86", "samples": "234", "features": "12889"}
    ]
  },
  "repeat": ["patients", "samples", "features"],
  "spec": {
    "title": {"text": {"repeat": "repeat"}},
    "mark": {"type": "arc"},
    "encoding": {
      "color": {
        "field": "site",
        "type": "nominal"
      },
      "theta": {"field": {"repeat": "repeat"}, "type": "quantitative"},
    }
  }
}

https://vega.github.io/editor/#/url/vega-lite/N4IgJghgLhIFygG4QDYFcCmBneBtUWAllBvCAMID2AEiADQgAO0hGAdlDnCAGz0hYIAW0YpsZAIwT+AMwzQ0AJ3HcAHAE4A7AAYQAXzoFipbuWoB5AAr9mUVhy4h1AFn6CRYxwCYJq2fKglFRANZy99QwFjMgBVcgAZAEEbFnZOSXCGd1Fgr10GOQVlR1UeHgBWCKMSWPIAZQAxFLs0kr4s4RzvAGZXAoCgxwkvVQ19AF0DEGVGALwmVIc3Ts9-IvFxrNmAY3hQOygxPZASAA8oY5m57ivofSmhCEUAa2OoAE9ZsifdqfZtyhgQhsADmxwBKEoimOMlYKDAZCINQYHy+3DYlCEwNQEROAAsMDAYXCEQhphhZncbhS5lNUSYQABHNAQDjEFiIUh6bl6IA

Checklist

• I checked for duplicate issues.

See https://vega-js.slack.com/archives/C4R371X41/p1707951282019609