📝 clarify async config docs

docs/api/async-logger-config-to-json.md

@@ -2,8 +2,8 @@
 name: async-logger-config-to-json
 group: api
 category: async
-update-time: 20260512
-description: Convert AsyncLoggerConfig into a JSON value for export, persistence, or generated async config output.
+update-time: 20260614
+description: Convert AsyncLoggerConfig into a JSON value for export, persistence, or generated async config output using the stable serialized policy labels.
 key-word:
     - async
     - config
@@ -36,6 +36,7 @@ Detailed rules explaining key parameters and behaviors
 - The output includes `max_pending`, `max_batch`, `linger_ms`, `overflow`, and `flush`.
 - Policy fields are serialized using the stable labels accepted by the config parser.
 - This helper exports effective typed config after constructor normalization has already happened.
+- If `max_pending` is negative in the config object, the exported JSON preserves that negative value because runtime queue clamping happens later, not during serialization.
 - The JSON shape matches the `async_config` section used by async build config parsing.
 
 ### How to Use
@@ -67,5 +68,13 @@ In this example, the exported JSON stays aligned with parser expectations.
 e.g.:
 - If `max_batch` or `linger_ms` were normalized during construction, the exported JSON reflects the normalized values rather than the original invalid inputs.
 
+- If callers need to understand runtime queue behavior for negative `max_pending`, they should document that separately because serialization preserves the config value rather than the later queue-kind clamp.
+
 - If callers want direct text output instead of a JSON value, they should use `stringify_async_logger_config(...)` instead.
 
+### Notes
+
+1. Serialized policy labels round-trip through `parse_async_logger_config_text(...)`.
+
+2. The serializer emits canonical labels like `DropNewest` and `Never`, even though the parser also accepts compatibility aliases such as `DropLatest` and `None`.
+