Plugin discovery exceptions in gateway startup (gateway/run.py) and
CLI startup (hermes_cli/main.py) are caught and logged at DEBUG
level, making them invisible at the default INFO log level.
If any plugin import fails — syntax error, missing dependency, import
cycle — operators get zero indication unless they bump the log level
to DEBUG. This makes broken plugins appear enabled but silently
non-functional.
Change both locations to logger.warning() so failures are visible at
production log levels.
Closes#28137
