tikzbox + draw + tikzpicture Konflikt

\documentclass[headheight=19pt]{scrartcl}
%------------------------------------------------------------------------------
\usepackage[utf8]{inputenc}
\usepackage[ngerman]{babel}
\usepackage[norndcorners,customcolors,nofill]{hf-tikz} 
\usepackage{tikz}
\usetikzlibrary{angles,babel,decorations,quotes}
\pgfdeclaredecoration{ignore}{final}
{
  \state{final}{}
}
%------------------------------------------------------------------------------
\newbox\mytikzbox 
\newcommand{\tikzBox}[2][\mytikzbox]{% 
   \sbox#1{\pgfinterruptpicture#2\endpgfinterruptpicture}}
%-------------------------------------------------------------------------------
\tikzstyle{mybox}=[draw=gray, fill=white!20, align=left,  text width = 0.9\linewidth]
\hfsetbordercolor{gray}

\tikzset{
  winkel/.style={draw=gray,angle eccentricity=.6,angle radius=1cm},
  mybox/.style={draw=gray,fill=white,align=left,text width=.9\linewidth}
}
%-------------------------------------------------------------------------------
\begin{document}
\begin{center}
  \begin{tikzpicture}
    \tikzBox{%
      \tikz[auto]
      \draw
        (2.5,0) coordinate[label=right:B] (B)
        -- node{$h$} 
        (-1,0) coordinate[label=left:A] (A)
        -- node{$g$} 
        (0,2) coordinate[label=above right:C] (C)
        decorate[decoration=ignore] { -- node{$a$} cycle}
        pic["$\alpha$", winkel]{angle=B--A--C}% Winkel bei Node A
        pic["$\beta$", winkel]{angle=C--B--A}% Winkel bei Node B
        pic["$\cdot$", winkel]{angle=A--C--B}% Winkel bei Node C
      ;
    }
    \node[mybox,rounded corners,font=\bfseries]
        {\parbox[t]{.6\linewidth}{%
            Das ist ein Text.
            }%
          \parbox[t]{.5\linewidth}{\centering%
          \raisebox{\dimexpr-\height+\ht\strutbox\relax}{\usebox\mytikzbox}}};
    \end{tikzpicture}
  \end{center}
\end{document}