📝 Add 1.0.1(0.6.1) change notes for wide file rotation

docs/api/file-rotation-config-to-json.md

@@ -33,8 +33,9 @@ pub fn file_rotation_config_to_json(config : FileRotation) -> @json_parser.JsonV
 
 Detailed rules explaining key parameters and behaviors
 
-- The output includes `max_bytes` and `max_backups`.
-- Both numeric fields are exported as JSON numbers.
+- The output always includes `max_bytes` and `max_backups`.
+- Both of those compatibility fields are exported as JSON numbers.
+- If the policy carries a wide threshold from `file_rotation_i64(...)`, the output also includes `max_bytes_i64` as a JSON string for exact roundtrip transport.
 - This helper serializes the rotation config object itself rather than sink availability, failure counters, or file state.
 - The same JSON shape is reused by `sink_config_to_json(...)`, file sink state export helpers, and larger logger config serialization paths.
 
@@ -61,6 +62,16 @@ let rotation_json = file_rotation_config_to_json(rotation)
 
 In this example, callers can carry the nested rotation shape without exporting a full sink config.
 
+#### When Need Exact Wide-threshold Roundtrip
+
+When a native large-file policy should preserve the original `Int64` threshold in JSON:
+```moonbit
+let rotation = file_rotation_i64(4294967296L, max_backups=2)
+let rotation_json = file_rotation_config_to_json(rotation)
+```
+
+In this example, the JSON value includes the compatibility `max_bytes` view plus `max_bytes_i64` as a string.
+
 ### Error Case
 
 e.g.:
@@ -73,3 +84,5 @@ e.g.:
 1. Use this helper when downstream code expects `JsonValue` rather than a typed `FileRotation` value.
 
 2. Pair it with `file_rotation(...)` when building rotation policy in code before export.
+
+3. For `file_rotation_i64(...)`, treat `max_bytes_i64` as the exact roundtrip field and `max_bytes` as the compatibility view.