Export themes from brand center

Theme Center has an API to export the theme that has been directly created in the Brand Center.

https://<tenant>.sharepoint.com/sites/brandcenter/_api/brandcenter/GetTenantThemes

This call will return all a theme in the following format:

{
    "@odata.context": "https://contoso.sharepoint.com/sites/brandcenter/_api/$metadata#SP.TenantThemes",
    "hideDefaultThemes": false,
    "themeData": [
        {
            "id": 83,
            "isThemesV2": false,
            "isVisible": true,
            "name": "Coffee Theme",
            "source": 1,
            "themeJson": "{\"name\":\"Coffee Theme\",\"isInverted\":true,\"palette\":{\"themeDarker\":\"#171f1d\",\"themeDark\":\"#2c3b37\",\"themeDarkAlt\":\"#415751\",\"themePrimary\":\"#C0FFEE\",\"themeSecondary\":\"#56736b\",\"themeTertiary\":\"#6b8f85\",\"themeLight\":\"#80ab9f\",\"themeLighter\":\"#95c7ba\",\"themeLighterAlt\":\"#aae3d4\",\"black\":\"#171f1d\",\"neutralDark\":\"#2c3b37\",\"neutralPrimary\":\"#C0FFEE\",\"neutralPrimaryAlt\":\"#56736b\",\"neutralSecondary\":\"#6b8f85\",\"neutralTertiary\":\"#80ab9f\",\"neutralTertiaryAlt\":\"#000000\",\"neutralLight\":\"#000000\",\"neutralLighter\":\"#000000\",\"neutralLighterAlt\":\"#000000\",\"white\":\"#000000\",\"neutralQuaternaryAlt\":\"#000000\",\"neutralQuaternary\":\"#000000\",\"accent\":\"#4F6BED\"}}"
        }
    ]
}

This call returns all the themes.

m365 spo theme list

This does not return any of the Brand Center specifc themes so either we should include these calls in the regular command or write a dedicated set of Brand Center calls. Thoughts?

Start with the m365 spo theme list command and the documented Brand Center GetTenantThemes endpoint. Review the existing theme-listing flow and the 16-comment discussion to determine whether Brand Center themes belong in the regular command or a dedicated command. Done means the chosen approach returns the Brand Center-specific themes without regressing existing theme results.