Update springignore to prevent circular reference in smoke tests

Added test-engine, .github, and build to springignore.txt to prevent
Spring's archive scanner from recursively scanning these directories
when SpringBoard is used as a game archive.

Also updated .gitignore to exclude test artifacts.

Author: claude

.gitignore

@@ -10,3 +10,8 @@ env/
 # don't track local (dev) file
 *.local
 *.7z
+
+# Test engine artifacts
+test-engine/games/
+test-engine/script.txt
+test-engine/test-data/

springignore.txt

@@ -2,4 +2,7 @@
 doc
 model
 issues
-dist_cfg
+dist_cfg
+test-engine
+.github
+build