📝 refine async shutdown docs

docs/api/async-logger-close.md

@@ -2,8 +2,8 @@
 name: async-logger-close
 group: api
 category: async
-update-time: 20260512
-description: Close the async logger queue and optionally clear pending records immediately.
+update-time: 20260614
+description: Close the async logger queue immediately and optionally convert current pending backlog into dropped records before queue closure.
 key-word:
     - async
     - logger
@@ -38,6 +38,7 @@ Detailed rules explaining key parameters and behaviors
 - `clear=false` closes the queue without explicitly abandoning pending records in the helper itself.
 - `clear=true` counts pending records as dropped and resets `pending_count` to `0` before closing the queue.
 - This helper does not itself wait for the worker to finish.
+- Because this is a low-level close primitive, it does not first run `wait_idle()` or apply the runtime-dependent fallback logic used by `shutdown()`.
 
 ### How to Use
 
@@ -66,6 +67,8 @@ In this example, queued backlog is counted as dropped instead of waiting for fur
 e.g.:
 - If `clear=true`, pending records are intentionally discarded and contribute to `dropped_count()`.
 
+- If `clear=false`, pending records may still exist after closure until worker drain or later cleanup resolves them.
+
 - If callers need graceful waiting for drain completion, `shutdown()` is usually the better API.
 
 ### Notes
@@ -73,3 +76,5 @@ e.g.:
 1. This is a low-level lifecycle helper; prefer `shutdown()` for normal graceful teardown.
 
 2. Use `clear=true` only when backlog loss is an acceptable shutdown tradeoff.
+
+3. Pair it with `pending_count()`, `dropped_count()`, or `state()` when you need to observe what happened to existing backlog after closure.

docs/api/async-logger-shutdown.md

@@ -38,6 +38,7 @@ Detailed rules explaining key parameters and behaviors
 - In runtimes where shutdown clearing after idle is enabled, remaining backlog after `wait_idle()` triggers a fallback `close(clear=true)`.
 - `clear=true` immediately closes and abandons pending records.
 - In runtimes where shutdown waits for workers, the method then waits until `is_running()` becomes `false` before returning.
+- In the current backend split, native-worker runtimes enable both the post-`wait_idle()` clear fallback and the final wait-for-worker phase, while compatibility runtimes skip both extra steps.
 
 ### How to Use
 
@@ -66,6 +67,8 @@ In this example, pending work is abandoned intentionally so shutdown can complet
 e.g.:
 - If `clear=true`, pending records are intentionally dropped rather than drained.
 
+- If `wait_idle()` returns early because the worker failed, shutdown behavior after that point still depends on the active runtime's fallback and worker-wait rules.
+
 - In compatibility-style runtimes without background-worker waiting, shutdown still closes the logger but may not perform the extra wait-for-worker phase described for native-worker runtimes.
 
 - If callers skip `shutdown()` and only inspect flags manually, it is easier to leave the worker lifecycle in an unclear state.
@@ -77,3 +80,5 @@ e.g.:
 2. Exact post-close waiting behavior depends on the active async runtime mode.
 
 3. Choose `clear=true` only when loss of queued records is acceptable.
+
+4. Pair it with `state()` or focused counters when tests need to assert whether shutdown drained backlog or converted it into dropped records.