✨ Add split sink routing helpers

docs/README-en.md

@@ -14,6 +14,7 @@ BitLogger currently provides:
 - context fields via `with_context_fields(...)`
 - optional timestamps via `with_timestamp()`
 - sink fanout via `fanout_sink(...)`
+- sink routing via `split_sink(...)` and `split_by_level(...)`
 - custom integration via `callback_sink(...)`
 - in-memory buffering via `buffered_sink(...)`
 - record filtering via `filter_sink(...)`
@@ -121,6 +122,25 @@ logger.info("three")
 ignore(logger.sink.flush())
 ```
 
+Level-based split sink:
+
+```moonbit
+let logger = Logger::new(
+  split_by_level(
+    callback_sink(fn(rec) {
+      println("high priority: \{rec.level.label()} \{rec.message}")
+    }),
+    console_sink(),
+    min_level=Level::Warn,
+  ),
+  min_level=Level::Trace,
+  target="split",
+)
+
+logger.info("normal output")
+logger.warn("warning output")
+```
+
 Custom text formatter:
 
 ```moonbit

docs/changes/0.3.0.md

@@ -29,6 +29,7 @@ version 0.3.0
 - feat: support formatter tokens `{timestamp}`, `{timestamp_ms}`, `{level}`, `{target}`, `{message}`, and `{fields}` in both runtime and JSON config paths
 - feat: add `FileRotation`, `file_rotation(...)`, and size-based file rotation with retained backups for `file_sink(...)`
 - feat: support `sink.rotation.max_bytes` and `sink.rotation.max_backups` in JSON logger config
+- feat: add `SplitSink`, `split_sink(...)`, and `split_by_level(...)` for routing records into different sinks by predicate or level
 
 ### Test
 
@@ -40,6 +41,7 @@ version 0.3.0
 - test: cover dropped-count reporting for bounded config-built queue
 - test: cover template-based formatter rendering and disabled token behavior
 - test: cover file rotation config parsing, config roundtrip, and native rotation behavior
+- test: cover split sink predicate routing and level-based routing behavior
 - test: add async logger lifecycle, config roundtrip, and batching/flush policy test seeds
 - build: verify `bitlogger_async --target native` and `examples/async_basic --target native` compile successfully
 
@@ -52,6 +54,7 @@ version 0.3.0
 - docs: update root README, English README, and Mooncake README with config usage notes
 - docs: update formatter examples to demonstrate template-based text rendering
 - docs: update file sink examples to demonstrate rotation and backup retention
+- docs: add split sink examples for level-based routing
 - docs: update root README and English README with async adapter notes and current scope
 - chore: ignore local `.mooncakes/` cache directory in git