✨ add wasm coverage and trace context

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

@@ -0,0 +1,21 @@
+---
+name: async-logger-with-trace-context
+group: api
+category: async
+update-time: 20260719
+description: Bind TraceContext fields before records enter an AsyncLogger queue.
+key-word:
+    - async
+    - trace
+    - context
+---
+
+## Async-logger-with-trace-context
+
+```moonbit
+let contextual = logger.with_trace_context(
+  @bitlogger.trace_context("trace-1", "span-1"),
+)
+```
+
+The helper stores the mapped fields on the returned async logger and preserves its queue, lifecycle, target, and threshold state. Context is added before records are enqueued.

docs/api/index.md

@@ -31,6 +31,7 @@ BitLogger API navigation.
 - [logger-with-timestamp.md](./logger-with-timestamp.md)
 - [logger-with-context-fields.md](./logger-with-context-fields.md)
 - [logger-bind.md](./logger-bind.md)
+- [logger-with-trace-context.md](./logger-with-trace-context.md)
 - [logger-with-filter.md](./logger-with-filter.md)
 - [logger-with-patch.md](./logger-with-patch.md)
 - [logger-with-queue.md](./logger-with-queue.md)
@@ -99,6 +100,10 @@ BitLogger API navigation.
 - [fields.md](./fields.md)
 - [text-formatter-config-type.md](./text-formatter-config-type.md)
 
+## Observability
+
+- [trace-context.md](./trace-context.md)
+
 ## Record and level
 
 - [record.md](./record.md)
@@ -266,6 +271,7 @@ BitLogger API navigation.
 - [async-logger-with-min-level.md](./async-logger-with-min-level.md)
 - [async-logger-with-timestamp.md](./async-logger-with-timestamp.md)
 - [async-logger-with-context-fields.md](./async-logger-with-context-fields.md)
+- [async-logger-with-trace-context.md](./async-logger-with-trace-context.md)
 - [async-logger-with-filter.md](./async-logger-with-filter.md)
 - [async-logger-with-patch.md](./async-logger-with-patch.md)
 
@@ -322,6 +328,7 @@ BitLogger API navigation.
 - [library-logger-child.md](./library-logger-child.md)
 - [library-logger-with-context-fields.md](./library-logger-with-context-fields.md)
 - [library-logger-bind.md](./library-logger-bind.md)
+- [library-logger-with-trace-context.md](./library-logger-with-trace-context.md)
 - [library-logger-is-enabled.md](./library-logger-is-enabled.md)
 - [library-logger-log.md](./library-logger-log.md)
 - [library-logger-info.md](./library-logger-info.md)
@@ -341,6 +348,7 @@ BitLogger API navigation.
 - [library-async-logger-child.md](./library-async-logger-child.md)
 - [library-async-logger-with-context-fields.md](./library-async-logger-with-context-fields.md)
 - [library-async-logger-bind.md](./library-async-logger-bind.md)
+- [library-async-logger-with-trace-context.md](./library-async-logger-with-trace-context.md)
 - [library-async-logger-is-enabled.md](./library-async-logger-is-enabled.md)
 - [library-async-logger-log.md](./library-async-logger-log.md)
 - [library-async-logger-info.md](./library-async-logger-info.md)

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.

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.

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

@@ -0,0 +1,22 @@
+---
+name: logger-with-trace-context
+group: api
+category: logger
+update-time: 20260719
+description: Bind a TraceContext to every record from a synchronous Logger.
+key-word:
+    - logger
+    - trace
+    - context
+---
+
+## Logger-with-trace-context
+
+```moonbit
+pub fn[S] Logger::with_trace_context(
+  self : Logger[S],
+  context : TraceContext,
+) -> Logger[ContextSink[S]]
+```
+
+Returns a derived logger that prepends the context fields to every record. The original logger is unchanged. This is equivalent to `with_context_fields(context.as_fields())`, while making trace intent explicit.

docs/api/trace-context.md

@@ -0,0 +1,25 @@
+---
+name: trace-context
+group: api
+category: observability
+update-time: 20260719
+description: Represent and bind distributed trace metadata using stable structured-log fields.
+key-word:
+    - trace
+    - context
+    - observability
+---
+
+## Trace-context
+
+`TraceContext` carries the standard log fields used to correlate records with distributed traces: `trace_id`, `span_id`, `trace_flags`, and optional `trace_state`.
+
+```moonbit
+let context = trace_context(
+  "4bf92f3577b34da6a3ce929d0e0e4736",
+  "00f067aa0ba902b7",
+  trace_state="vendor=value",
+)
+```
+
+Use `context.as_fields()` when integrating with a custom carrier, or pass the value to a logger's `with_trace_context(...)` helper. BitLogger does not parse HTTP headers or export OTLP data; an application-owned tracing library remains responsible for propagation and sampling.