Normalize encoded URL paths.

[samuel-williams-shopify]

Summary

• add conservative Protocol::URL::Path#normalize behavior based on the path segment grammar
• decode percent-encoded unreserved characters and uppercase retained percent escapes
• preserve literal and encoded reserved-character distinctions
• percent encode literal characters outside the path segment grammar
• reject malformed escapes, NUL, and invalid string encodings
• preserve path structure so simplify remains an explicit application-level operation

Testing

• bundle exec bake test
• bundle exec rubocop lib/protocol/url/path.rb test/protocol/url/path.rb

Performance

The direct normalization pass is approximately 1.1-2.2x faster than decode/re-encode on representative paths and allocates substantially fewer objects.