gitignore: cover test frame dumps written into the project root, not just harness/mame/

.gitignore

@@ -48,3 +48,7 @@ video/
 
 # Private MAME cfg for run.sh net (holds the per-device network provider; refreshed each run)
 harness/mame/cfg-net/
+
+# Test frame dumps written into the project root (the harness ignores them under harness/mame/)
+/*.ppm
+/*.pgm