fix: only set logging level when explicitly requested

[haoyu-haoyu]

Summary

download(), install_corenlp(), and Pipeline.__init__() all called set_logging_level() unconditionally, even when the caller passed neither logging_level nor verbose. This caused set_logging_level(None, None) to reset the stanza logger to INFO as a side effect, overriding any logging configuration the user had set up.

Closes #1418

Problem

import logging
import stanza

# User configures logging to WARNING
stanza.logger.setLevel('WARNING')

# This silently resets it to INFO
stanza.download('en')

# User's WARNING level is gone
print(stanza.logger.level)  # 20 (INFO), not 30 (WARNING)

Fix

Guard all three call sites so set_logging_level() is only invoked when the caller explicitly passes logging_level or verbose:

# Before (always called, even with defaults):
set_logging_level(logging_level, verbose)

# After (only when user requested):
if logging_level is not None or verbose is not None:
    set_logging_level(logging_level, verbose)

Files changed

File	Call site
stanza/resources/common.py	download()
stanza/resources/installation.py	install_corenlp()
stanza/pipeline/core.py	Pipeline.__init__()

Backward compatibility

• Users who pass logging_level='DEBUG' or verbose=True get the same behavior as before
• Users who don't pass either argument no longer have their logging silently reset
• stanza.download('en', logging_level='ERROR') still works