✨ add wasm coverage and trace context

docs/api/library-async-logger-with-trace-context.md

@@ -0,0 +1,15 @@
+---
+name: library-async-logger-with-trace-context
+group: api
+category: facade
+update-time: 20260719
+description: Bind TraceContext fields through the restricted LibraryAsyncLogger facade.
+key-word:
+    - library
+    - async
+    - trace
+---
+
+## Library-async-logger-with-trace-context
+
+`LibraryAsyncLogger::with_trace_context(...)` returns a derived library facade with `trace_id`, `span_id`, `trace_flags`, and optional `trace_state` attached to each later record. It does not start a worker or change lifecycle state.