By: ValentinHirschi <valentin.hirschi@gmail.com>
docs: open sewn initial states in the portal graph renderer 4cfcc9875 moved tests/resources/graphs/epemttbar.dot to the FeynKit DOT dialect, in which each initial-state connection of a cross section is one paired edge carrying its leg in an `external` statement instead of a pair of external vertices. The portal renderer drew those edges as propagators, so the e+ e- -> t tbar figure became a closed vacuum graph. Open such edges as FeynKit's own drawing (FeynmanDiagram::to_linnest) does: an incoming leg at the sink and an outgoing leg at the source, both tagged with the connection for cross-section placement. Graphs without sewn externals are unchanged; only the two epem-ttbar-cut SVGs differ. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>