Dwarf arts: Kanonenschuss stuns without knockback, Mörsergranate radius grows

Kanonenschuss: the stun no longer plays the hit motion or pushes the
target; stunned creatures stand still for 1.5 s. The impact effect only
shows on targets that did not resist, and the ray reaches 1800 for the
wider view. Mörsergranate: the impact radius grows by a tenth of its size
every 5 skill levels. Art levels come from a shared helper.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

CMakeLists.txt

@@ -60,6 +60,7 @@ add_library(sacredK SHARED
     src/mods/combos.cpp
     src/mods/aurahits.cpp
     src/mods/chainlightning.cpp
+    src/mods/dwarfarts.cpp
     src/mods/arttooltip.cpp
     src/mods/escape.cpp
     src/mods/recordcache.cpp