message: fix: create a PillCandidatePart on the beginning of a part string
diff: @@ -189,7 +189,13 @@ abstract class PlainBasePart extends BasePart {
  if (chr !== "@" && chr !== "#" && chr !== ":" && chr !== "+") {
  return true;
  }
  - // only split if the previous character is a space
  +
  + // split if we are at the beginning of the part text
  + if (offset === 0) {
  + return false;
  + }
  +
  + // or split if the previous character is a space
  // or if it is a + and this is a :
  return this._text[offset - 1] !== " " &&
  (this._text[offset - 1] !== "+" || chr !== ":");
  