This commit fixes two issues that caused build failures in GitHub:

1. JSR-512 Main Method Detection

Problem: Tests failed with error:
"The specified mainClass doesn't contain a main method with
appropriate signature"

JSR-512 (Java 21+) allows flexible main methods that can be
non-public and instance methods. The original code used
getMethod() which only finds PUBLIC methods, causing it to
fail when searching for package-private main methods.

Solution:
- Changed from getMethod() to getDeclaredMethod() for JSR-512
- Added setAccessible(true) for non-public method invocation
- Created findMethod() helper that searches class hierarchy
- Validates return type is void (JSR-512 requirement)
- Maintains correct priority order:
  1. static void main(String[]) - traditional
  2. static void main() - JSR-512 static no-args
  3. void main(String[]) - JSR-512 instance with args
  4. void main() - JSR-512 instance no-args

2. SystemExitException Logging

Problem: Integration tests expected [ERROR] log prefix for
SystemExitException but it was missing.

When SystemExitException was thrown during method invocation,
it got wrapped in InvocationTargetException and bypassed the
logging code.

Solution:
- Added special handling in InvocationTargetException catch
- Detects SystemExitException in the cause chain
- Logs with appropriate level (ERROR for non-zero exit codes)
- Re-throws the exception to maintain expected behavior