📝 clarify async state snapshot docs

docs/api/async-logger-state-new.md

@@ -56,6 +56,7 @@ Detailed rules explaining key parameters and behaviors
 - The constructed value matches the same public shape used by async logger serializers.
 - Because `AsyncLoggerState` is only a data snapshot type, this constructor is mainly useful for tests, adapters, and synthetic diagnostics rather than ordinary logger inspection.
 - Serialization helpers accept any `AsyncLoggerState` value, including hand-built ones from this constructor.
+- That includes combinations such as `has_failed=true` together with non-zero `pending_count` or a retained `last_error`, which are valid for diagnostic snapshots and test fixtures.
 
 ### How to Use
 
@@ -106,6 +107,8 @@ e.g.:
 
 - If callers manually combine a runtime snapshot, counters, or flush policy that do not actually belong together, the constructor still accepts that synthetic snapshot.
 
+- This constructor does not apply cleanup semantics such as clearing `last_error` on restart or draining pending records; callers must provide those fields exactly as they want them represented.
+
 ### Notes
 
 1. Use this helper when code should construct an `AsyncLoggerState` value explicitly.