For content items of mime_type text/html, the convention in
OpenACS is to store in the contents of the attribute "text"
the detailed mime-type as well. So instead of "hello world",
use "{{hello world" text/html}"
Technically the contents are a tcl list with two elements.
On import/export of xowiki, this field is not interpreted.
So change your generation script to:
::xowiki::Page create ::48865 -noinit \
...
-set text {{
Hallo - Willkommen..
} text/html} \
...
