Update test runner to use unit test files and make test scripts executable

Make test runner search in the unit/ subdirectory and ensure test scripts are executable for better test suite organization and reliability.

Author: vgrichina

test/test_runner.sh

@@ -15,7 +15,7 @@ TEST_NUMBER=0
 echo "TAP version 13"
 
 # Find all consolidated test files (we now have one file per CLI tool)
-test_files=("$TEST_DIR"/test_*.sh)
+test_files=("$TEST_DIR"/unit/test_*.sh)
 total_test_files=${#test_files[@]}
 echo "1..$total_test_files"
 
@@ -59,4 +59,4 @@ if [ $TESTS_FAILED -gt 0 ]; then
     exit 1
 fi
 
-exit 0
+exit 0