fix(linetype): DRAINAGE linetypes draw their arrows

The bundled DRAINAGE / DRAINAGE2 definitions use the RIGHT_ARROW shape
from qcadshp.shx, which had no substitute, so they drew as continuous
lines. Add it to the bundled shape set alongside BAT, ZIG and the rest.

Fixes #665

Co-Authored-By: Claude Opus 5.5 <[email protected]>

assets/fonts/ltypeshp.lff

@@ -43,3 +43,6 @@
 
 [009F] PLANT6
 0,0;2.58,-0.5;3.81,1.37;4.42,0
+
+[003C] RIGHT_ARROW
+0.5,0.5;0,0;0.5,-0.5