fix(scripts): exclude common Python environment dirs from validate:skills warnings

[WilliamBerryiii]

Problem

npm run validate:skills exits with code 1 due to -WarningsAsErrors when common Python environment directories (.hypothesis, .pytest_cache, .ruff_cache, .venv) exist inside skill folders. These are standard tool artifacts and should not trigger unrecognized-subdirectory warnings.

Currently affects the powerpoint skill under .github/skills/experimental/powerpoint/.

Expected Behavior

The validate:skills script should recognize .hypothesis, .pytest_cache, .ruff_cache, and .venv as known Python environment directories and exclude them from the unrecognized-subdirectory check. This eliminates false-positive warnings in local development and CI environments where these directories are present.

Acceptance Criteria

• Update Test-PythonSkillConfig or the relevant validation function in the skills validation script to allow .hypothesis, .pytest_cache, .ruff_cache, and .venv as known subdirectories
• npm run validate:skills passes with exit code 0 when these directories are present
• npm run lint:all achieves full clean exit (exit code 0)