📝 refine async policy docs

docs/api/async-overflow-policy.md

@@ -2,8 +2,8 @@
 name: async-overflow-policy
 group: api
 category: async
-update-time: 20260613
-description: Public overflow policy alias used by AsyncLoggerConfig and async queue behavior.
+update-time: 20260614
+description: Public overflow policy alias used by AsyncLoggerConfig, async parser labels, and runtime queue behavior.
 key-word:
     - async
     - overflow
@@ -34,6 +34,8 @@ Detailed rules explaining key parameters and behaviors
 - `AsyncOverflowPolicy::DropOldest` lets the underlying async queue discard older pending records when capacity is limited.
 - `AsyncOverflowPolicy::DropNewest` discards the incoming record instead of blocking.
 - The same enum is used by `AsyncLoggerConfig::new(...)`, async config parsing, and the queue-kind mapping inside `AsyncLogger`.
+- Async config parsing accepts the canonical label `DropNewest` and also the compatibility alias `DropLatest`, both mapping to the same public enum variant.
+- When `try_put(...)` reports that a record was not accepted under a drop policy, `dropped_count()` increases for that rejected enqueue.
 
 ### How to Use
 
@@ -64,8 +66,12 @@ e.g.:
 
 - Under drop policies, sustained overload increases `dropped_count()` instead of guaranteeing delivery.
 
+- The precise record discarded by the underlying queue behavior depends on the selected policy and queue implementation, so callers should not assume `dropped_count()` alone identifies which message was lost.
+
 ### Notes
 
 1. This policy applies to `bitlogger_async`, not synchronous `QueuedSink`.
 
 2. Choose `Blocking` only when producer-side waiting is acceptable for the caller.
+
+3. Serialized config uses the canonical `DropNewest` label even though the parser also accepts `DropLatest`.