audio-helper v1.5.6

Maintenance

• Apply the project coding standards across the package and tests/:
  Numpy-style docstrings on every function/class (including private and
  nested helpers), full type annotations with from __future__ import annotations, and comment density raised above the floor in every
  module. No public API or behavior changes.
• Route library logging through the os-helper logging surface
  (osh.info/warning/error) and adopt os-helper path/file utilities
  more widely; pin os-helper>=1.5.0.
• Refresh the project logo asset.