The Markdown inline scanner (parseInlineSpans) treats _ and * as
italic delimiters. A placeholder like {{project.case_number}} fed
through the scanner had its underscores consumed as italic markers,
leaving {{project.casenumber}} in the composed OOXML. The v1
placeholder pass then looked up the wrong key, surfacing
[KEIN WERT: project.casenumber] in the preview. The form ↔ preview
highlighting also stopped working because data-var attributes
mismatched between the input (snake_case) and the rendered span
(stripped).
parseInlineSpans now detects {{ at the cursor and skips ahead to
the matching }}, copying the entire placeholder verbatim into the
current text run. Unmatched {{ falls through to the existing
character handling so legal prose with stray braces still renders.
Tests: regression test for underscored keys (single + multiple +
mixed-with-italics), direct guard on parseInlineSpans, and an
italic-around-placeholder structural test.