Fix import guard to allow library usage

[hyeeyoungkim]

Summary

• Wrap args = parser.parse_args() and main(args) (lines 1693-1694) in an
  if __name__ == "__main__": guard so that import yesc no longer triggers
  argument parsing and execution

Problem

The debug lines at the end of yesc.py sit at module level (outside the
if __name__ guard), which means any import yesc immediately calls
parser.parse_args() and main(args). This prevents using yesc as a library
— for example, building args programmatically and calling main(args) from
another script.

The commented-out try/except block (lines 1682-1691) was the original
implementation inside the guard. The current lines were placed at module level
for debugging and left in place.

Change

Add if __name__ == "__main__": guard around lines 1693-1694 and indent them.
The ''' string literal on line 1691 exits the original if __name__ block
(it's at column 0), so these lines need their own guard rather than indenting
into the existing one.

Impact

• CLI usage (python yesc.py ...): No change — __name__ is "__main__",
  guard fires as before
• PyInstaller executable (yesc.exe): No change — same reason
• Library import (from yesc import main): Now works without side effects