[Copilot]

This change adds version-compare restore support by generating revert JSON OT from any two JSON documents. Given current and previous, the library can now emit an operation that transforms current back to previous, including full-document restores.

• What this enables

  • Introduces a Diff API on JSONOperationTransformer to generate OT from from -> to
  • Supports revert/rollback flows without requiring pre-recorded inverse operations
  • Handles arbitrary root document types, not just object subtrees

• Diff generation

  • Diffs objects recursively by key
  • Emits na for numeric deltas where possible
  • Falls back to subtree replacement for incompatible shape changes and array length changes
  • Produces valid OT for both nested fields and root-level document replacement

• Root-level OT support

  • Extends apply logic to handle p: []
  • Allows whole-document replace/delete/insert semantics when the revert target changes document type
  • Updates operation serialization/validation so root-scoped operations round-trip correctly

• Docs

  • Adds Diff usage to README.md and README.zh-CN.md
  • Documents revert/version-restore usage and subtree replacement fallback behavior

ot := jsonot.NewJSONOperationTransformer()

current, _ := jsonot.UnmarshalValue([]byte(`{"version":2,"items":[1,2,3]}`))
previous, _ := jsonot.UnmarshalValue([]byte(`{"version":1,"items":[1,3]}`))

revertOp := ot.Diff(context.Background(), current, previous)
restored := ot.Apply(context.Background(), current, revertOp.MustGet())