bug: `plugboard server` discovery command fails if venv is present

[toby-coleman]

Summary

Cannot run discover command if the supplied directory contains a.venv folder. Hidden folders should be ignored when searching for code files.

Version Information

Plugboard version: 0.7.0
Platform: macOS-26.5-arm64-arm-64bit-Mach-O
Python version: 3.13.9