docs(fixture): explain intentional SIMPLE_RIGHT_TRUE type at bypass merge switch

Added inline XML comment at (52,20) switch to explain why it uses
SIMPLE_RIGHT_TRUE while other south layer-3 merge switches use
SIMPLE_RIGHT_FALSE: this switch needs segment D accessible for the
Y=22 car-train terminal siding track (added in this PR).

Addresses review feedback "changed switches orientation (segments?)".

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: bedaHovorka

core-test/src/commonMain/resources/cz/vutbr/fit/interlockSim/xml/fixtures/praha-hlavni-nadrazi.xml

@@ -139,6 +139,7 @@
   <!-- South Layer 3 switches - MERGE switches (tracks converge here) -->
   <RailSwitch X="52" Y="4" SpatialType="HORIZONTAL" Type="SIMPLE_RIGHT_FALSE"/>
   <RailSwitch X="52" Y="12" SpatialType="HORIZONTAL" Type="SIMPLE_RIGHT_FALSE"/>
+  <!-- SIMPLE_RIGHT_TRUE (not FALSE): bypass row needs segment D for the Y=22 car-train terminal siding -->
   <RailSwitch X="52" Y="20" SpatialType="HORIZONTAL" Type="SIMPLE_RIGHT_TRUE"/>
 
   <!-- South Layer 4 signals (between merge and diverge switches) -->