♻️ Harden async logger lifecycle semantics

docs/README-en.md

@@ -176,6 +176,8 @@ if native_files_supported() {
 - A separate `bitlogger_async/` package is now included.
 - It uses `moonbitlang/async` and provides `AsyncLogger`, `async_logger(...)`, a background `run()` worker, and bounded async queue delivery.
 - The current async API already supports `with_context_fields(...)`, `with_filter(...)`, `with_patch(...)`, `with_target(...)`, and `child(...)`.
+- `shutdown()` is now the recommended way to stop the async worker. By default it waits for the queue to drain, closes the queue, and then waits for the worker to exit.
+- Basic lifecycle observability is also available through `is_closed()`, `is_running()`, `has_failed()`, and `last_error()`.
 - The recommended startup pattern is shown in [examples/async_basic/main.mbt](/E:/repo/MooLiteyukiBot/examples/async_basic/main.mbt:1).
 - This layer currently targets `native/llvm` only and remains isolated from the synchronous logger core.
 

docs/changes/0.3.0.md

@@ -17,6 +17,7 @@ version 0.3.0
 - feat: add `AsyncLogger`, `async_logger(...)`, `run()`, `wait_idle()`, `close()`, `pending_count()`, and `dropped_count()` on top of `moonbitlang/async`
 - feat: add async logger composition helpers `with_context_fields(...)`, `with_filter(...)`, `with_patch(...)`, `with_target(...)`, `child(...)`, and `with_timestamp(...)`
 - feat: add `AsyncLoggerBuildConfig`, `parse_async_logger_build_config_text(...)`, and `build_async_logger(...)` for config-driven async logger assembly
+- feat: add async lifecycle helpers `shutdown()`, `is_closed()`, `is_running()`, `has_failed()`, and `last_error()` for safer worker teardown and observability
 - feat: expose `Record::new(...)` for adapter and integration layers
 - fix: repair native file backend FFI declarations so native target checks succeed again
 - feat: support config keys `min_level`, `target`, `timestamp`, `sink.kind`, `sink.path`, `sink.append`, `sink.auto_flush`, `sink.text_formatter`, and `queue`