refactor: rename CxLLM-LB project + target to CxLLM-LIB

The directory was already named CxLLM-LIB but the .xcodeproj, target,
product name, and built dylib used the abbreviated 'CxLLM-LB' form.
Rename the project bundle, all internal pbxproj references, and the
Aggregate workspace pointer so naming is consistent everywhere.