[Mística] Evolve the token script to support per-corner border radius #1752

The current token script generates a single border radius value per token, which is applied to all four corners. At Mística, we need to evolve how we manage border radius so that each corner can be set independently. The first use case is the Message component bubble, where one corner has a different radius from the other three. The different corner can be any of the four (top-left, top-right, bottom-right or bottom-left), and the values depend on the skin.

This requires a change in the token architecture and in the script that parses and exports the tokens.

Example of the expected structure

The following example is illustrative. The final structure is to be validated by the development team. Values are placeholders, as they depend on the skin.

"radius": {
  "bubble": {
    "topLeft":     { "value": "4",  "type": "borderRadius" },
    "topRight":    { "value": "24", "type": "borderRadius" },
    "bottomRight": { "value": "24", "type": "borderRadius" },
    "bottomLeft":  { "value": "24", "type": "borderRadius" }
  }
}

Objective

Update the token script so it can read, validate and export border radius tokens defined per corner, while keeping backward compatibility with existing uniform radius tokens.