Escape literal percent signs in CLI help strings, add CODEOWNERS

[mikelangmayr]

• every CLI command crashed at startup on Python 3.14 with "ValueError: badly formed help string"; 3.14 expands argparse help, so the literal % in three help strings parsed as a format spec
• escaped them as %%, so --help still renders a single %
• adds .github/CODEOWNERS with @mikelangmayr @scizen9 @prkrtg, matching hispec's
• verified on Python 3.14.4 that the old string raises and the new one renders; suite passes on 3.12