I would like to be warned when a select setting's default value is not a valid option.

Describe the solution you'd like
Writing this setting in a block/section/settings_schema.json should warn me that the default doesn't match the options.

  "settings": [
    {
      "type": "select",
      "id": "alignment",
      "default": "this-is-not-an-option", 
      "options": [
        { "value": "flex-start", "label": "t:options.alignment.left" },
        { "value": "center", "label": "t:options.alignment.center" },
        { "value": "flex-end", "label": "t:options.alignment.right" }
      ],
    },

Similarly, I'd like the presets to warn me as well if a setting value in a preset is not a valid option.

  "presets": [
    {
      "name": "t:general.column",
      "category": "t:general.layout",
      "settings": {
        "layout_direction": "group--vertical",
        "alignment": "this-is-not-an-option",
      }
    },

Locate the validation entry point for block/section/settings_schema.json and read how select settings and presets are currently checked. Add warnings for defaults and preset values that do not match the declared options, then verify both examples produce warnings.