Document Zeitwerk edge-case audit for decorators and overrides

[kitcommerce]

Summary

• add WA-VERIFY-111 verification notes for decorator, override, and extension-point Zeitwerk compatibility
• catalog the core patterns used by downstream Workarea implementations
• document the existing core-side to_prepare requires as a contained autoload workaround rather than a downstream compatibility break

Testing

• attempted ./scripts/verify-zeitwerk.sh (fails in this environment before Rails boots because Bundler rejects required_ruby_version from workarea.gemspec under the available Ruby/Bundler combination: Illformed requirement [\">= 2.7.0, < 3.5.0\"])
• targeted source audit of decorator, override, to_prepare, preview loading, and custom autoload-path code paths

Client impact

• None expected