fix(rendering): alpha-to-coverage for hair, skip eye glow geosets, add missing include

- Enable alpha-to-coverage on alphaTestPipeline for smooth hair edges
  when MSAA is active (both init and recreatePipelines paths)
- Shader uses fwidth()-based alpha rescaling for clean coverage
- Skip group 17/18 geosets (DK/NE eye glow) when no geoset filter is
  set — prevents blue eye glow on all NPCs
- Add missing <libgen.h> include for dirname() on Linux

src/main.cpp

@@ -15,6 +15,7 @@
 #include <X11/Xlib.h>
 #include <execinfo.h>
 #include <unistd.h>
+#include <libgen.h>
 #include <cstring>
 
 // Keep a persistent X11 connection for emergency mouse release in signal handlers.