Remove dead .clang-format/.clang-tidy fallback chain in format.ps1

[python-processing-unit]

Problem

format.ps1:36-50 implements a 3-tier config file lookup (env var, repo file, hardcoded defaults) for .clang-format and .clang-tidy. Both files are confirmed absent; the lookup is dead configurability.

Fix

Hardcode the defaults and remove ~15 lines of unused lookup logic.

Reported by Kilo Code (automated audit tool), not a human reviewer.