Issue: Closes #519 “/claim #519”

What’s implemented

Migration[A,B] typed façade with apply, ++, reverse. DynamicMigration core ADT (fully serialisable) and all required MigrationActions. Macro‑driven selector extraction (_.field, _.items.each, _.country.when[“UK”]). Builder API (Migration.newBuilder…) with compile‑time validation. Structural reverse (reverse) and best‑effort inverse semantics. Comprehensive ZIO‑Test suite (MigrationSpec) covering records, enums, collections, and the three laws (identity, associativity, reverse‑inverse). JSON (de)serialization support via derived ZIO‑Schema. The attached screen‑capture video (migration-demo.mp4) shows the migration being built, applied to a concrete value, and the test suite passing .Run sbt ++2.13.12 test and sbt ++3.5.0 test. All tests passed. /claim #519