/claim #679

This PR implements the full JSON ADT for ZIO Blocks as defined in Bounty #679.

Core Features Implemented

• Added Json sealed trait with 6 cases (Object, Array, String, Number, Boolean, Null)
• Implemented JsonError with DynamicOptic path tracking and detailed error accumulation
• Implemented JsonSelection API for fluent, multi-value navigation with accumulated errors
• Added MergeStrategy sealed hierarchy (Auto, Deep, Shallow, Replace, Concat, Custom)
• Implemented complete DynamicOptic path navigation (get / modify / set / delete)
• Added transformation operations: transformUp, transformDown, filter, filterNot
• Implemented normalization operations: sortKeys, dropNulls, dropEmpty
• Added JsonEncoder[A] and JsonDecoder[A] type classes with priority resolution
• Integrated parser support via Json.parse(String | Array[Byte])
• Added encoding methods: json.encode and json.encodeToBytes
• Implemented bidirectional DynamicValue interop

Code Summary

Total implementation: ~1250 LOC across 4 Scala files
All components manually verified and syntactically validated.

Closes #679