Example files like openai.py shadow installed packages when Python adds the
script directory to sys.path. Prepend the parent folder name to each example
file (e.g. openai.py -> function-calling-openai.py). Also split
thinking-and-mcp/ into separate mcp/ and thinking/ directories.
Replace the nested services/speech/ and services/function-calling/ with
top-level voice/ and function-calling/ directories. Update eval script
paths and README to match.