✨ add wasm coverage and trace context

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

@@ -0,0 +1,20 @@
+---
+name: library-logger-with-trace-context
+group: api
+category: facade
+update-time: 20260719
+description: Bind TraceContext fields through the restricted LibraryLogger facade.
+key-word:
+    - library
+    - trace
+    - context
+---
+
+## Library-logger-with-trace-context
+
+```moonbit
+let logger = LibraryLogger::new(console_sink())
+  .with_trace_context(trace_context("trace-1", "span-1"))
+```
+
+The derived facade preserves its library-facing API while wrapping the sink with context fields. Use `to_logger()` only when broader composition is required.