docs: add tests/ folder convention for test output

.gitignore

@@ -9,7 +9,21 @@ build
 /sandbox-test/test_results.json
 
 # Test output files
-screenshot_*.png
+/tests/
+*.png
 test_*.json
 test_*.txt
 test_*.log
+*_hierarchy.json
+recorded_actions.json
+
+# Duplicate asset folders (use src/main/assets/ instead)
+/icons/
+/scripts/
+/ui/
+
+# Sandbox data created during testing
+/src/main/assets/sandbox_data/
+
+# Misc
+NUL