📝 clarify root async builder docs

docs/api/build-async-logger.md

@@ -40,6 +40,8 @@ Detailed rules explaining key parameters and behaviors
 - The returned sink type is `RuntimeSink`, which keeps configured control helpers available where relevant.
 - This builder returns the underlying `AsyncLogger[@bitlogger.RuntimeSink]` value directly. `build_application_async_logger(...)` only re-exports the same result under the `ApplicationAsyncLogger` alias, while `build_library_async_logger(...)` wraps the same result in `LibraryAsyncLogger[@bitlogger.RuntimeSink]`.
 - Because this path starts from `build_logger(config.logger)`, it preserves the broader runtime-sink build path, including sync-side queue decoration when `LoggerConfig.queue` is present.
+- In the current direct builder coverage, the returned logger exposes the expected serialized async state snapshot, runtime-sink variant choice, queue counters, lifecycle flags, and later failure fields after `run()` or `shutdown()`.
+- File-backed runtime helpers also stay directly available on the returned `RuntimeSink` with the same behavior later observed through the application and library facade equivalence tests.
 - Use `build_async_text_logger(...)` instead when you want the direct text-console async builder path with `FormattedConsoleSink` and without the sync runtime-sink construction layer.
 - The `src-async` library is designed to compile on `native / llvm / js / wasm / wasm-gc`, but runtime mode differs by backend.
 - Current local release-facing verification is explicit for `native / js / wasm / wasm-gc`.
@@ -83,6 +85,8 @@ e.g.:
 
 - If the configured sink shape is unsupported for a specific capability, the resulting runtime behavior follows the existing sink/runtime rules rather than inventing a separate builder-only failure model.
 
+- If callers depend on queued runtime-sink helpers or file-backed runtime helpers, this builder is the direct API that preserves them rather than a reduced facade path.
+
 ### Notes
 
 1. Prefer this API when applications externalize both sync sink choice and async queue behavior.

docs/api/build-async-text-logger.md

@@ -39,6 +39,7 @@ Detailed rules explaining key parameters and behaviors
 - Unlike `build_async_logger(...)`, this helper does not run the full synchronous `build_logger(config.logger)` path first.
 - That means it uses `config.logger.sink.text_formatter`, `min_level`, `target`, and `timestamp` directly, but it does not apply `LoggerConfig.queue` or preserve other sync runtime sink controls.
 - This builder returns the underlying `AsyncLogger[@bitlogger.FormattedConsoleSink]` value directly. `build_application_text_async_logger(...)` only re-exports that same result under the `ApplicationTextAsyncLogger` alias, while `build_library_async_text_logger(...)` wraps the same result in `LibraryAsyncLogger[@bitlogger.FormattedConsoleSink]`.
+- In the current direct text-builder coverage, the returned logger exposes the expected serialized async state snapshot, formatter behavior, queue counters, lifecycle flags, and later failure fields after worker execution.
 - The async `flush_policy` still comes from `config.async_config`, but this text-specific builder does not supply the explicit `flush=fn(sink) { sink.flush() }` callback used by `build_async_logger(...)`.
 - In practice, `Batch` and `Shutdown` therefore only trigger the default no-op async flush callback on this path, while each record write still follows whatever immediate behavior `FormattedConsoleSink` already has on its own.
 - This helper is best suited to text-console output paths where callers want the concrete formatted sink type instead of `RuntimeSink`.
@@ -69,6 +70,8 @@ e.g.:
 
 - If the logger is never `run()`, pending records still follow the normal async queue lifecycle rules.
 
+- If callers rely on the concrete formatter or post-run state shape, this builder is the direct API that preserves those text-console details rather than a reduced alias or wrapper.
+
 ### Notes
 
 1. This API is narrower than `build_async_logger(...)` because it preserves a concrete text sink type.