📝 document sync config model aliases

docs/api/logger-config-type.md

@@ -0,0 +1,71 @@
+---
+name: logger-config-type
+group: api
+category: config
+update-time: 20260613
+description: Public logger config alias used for serializable top-level sync logger settings.
+key-word:
+    - logger
+    - config
+    - alias
+    - public
+---
+
+## Logger-config-type
+
+`LoggerConfig` is the public top-level serializable config type used to describe sync logger behavior. It is a direct alias to the logger config model used by config parsers, sync logger builders, and async build config embedding.
+
+### Interface
+
+```moonbit
+pub type LoggerConfig = @utils.LoggerConfig
+```
+
+#### output
+
+- `LoggerConfig` - Public logger config object containing `min_level`, `target`, `timestamp`, `sink`, and optional `queue`.
+
+### Explanation
+
+Detailed rules explaining key parameters and behaviors
+
+- This is a type alias, not a built logger instance.
+- The current fields are `min_level : Level`, `target : String`, `timestamp : Bool`, `sink : SinkConfig`, and `queue : QueueConfig?`.
+- `LoggerConfig::new(...)` constructs this type as the main sync config entry point.
+- `parse_logger_config_text(...)`, `logger_config_to_json(...)`, `stringify_logger_config(...)`, and `build_logger(...)` all consume or produce the same public config shape.
+
+### How to Use
+
+Here are some specific examples provided.
+
+#### When Need A Typed Top-level Logger Policy
+
+When sync logger settings should remain structured config data before runtime construction:
+```moonbit
+let config : LoggerConfig = LoggerConfig::new(target="svc")
+```
+
+In this example, the logger setup stays as a typed config object instead of becoming a runtime logger immediately.
+
+#### When Need To Inspect Or Export Full Sync Logger Settings
+
+When configuration should be reviewed or serialized before build time:
+```moonbit
+let config = LoggerConfig::new(queue=Some(QueueConfig::new(16)))
+println(stringify_logger_config(config, pretty=true))
+```
+
+In this example, the same public config type supports both inspection and later runtime assembly.
+
+### Error Case
+
+e.g.:
+- `LoggerConfig` itself does not have a runtime failure mode.
+
+- A valid config object can still describe a sink shape whose eventual runtime behavior depends on backend support, such as file output on limited targets.
+
+### Notes
+
+1. Use `LoggerConfig::new(...)` when you need a value of this type in code.
+
+2. Use `ConfiguredLogger` or `Logger` only after a build step when runtime logging behavior is actually needed.