📝 document record alias

docs/api/index.md

@@ -79,6 +79,7 @@ BitLogger API navigation.
 
 ## Record and level
 
+- [record.md](./record.md)
 - [record-new.md](./record-new.md)
 - [level.md](./level.md)
 - [level-priority.md](./level-priority.md)

docs/api/record.md

@@ -0,0 +1,73 @@
+---
+name: record
+group: api
+category: record
+update-time: 20260613
+description: Public record alias used across formatting, filtering, sinks, and logger output paths.
+key-word:
+    - record
+    - alias
+    - logging
+    - public
+---
+
+## Record
+
+`Record` is the public log-event data type used throughout BitLogger. It is a direct alias to the core record model, so formatters, predicates, sinks, patches, and callback-based integrations all share the same structured event shape.
+
+### Interface
+
+```moonbit
+pub type Record = @core.Record
+```
+
+#### output
+
+- `Record` - Public structured log-event value containing `level`, `timestamp_ms`, `target`, `message`, and `fields`.
+
+### Explanation
+
+Detailed rules explaining key parameters and behaviors
+
+- This is a type alias, not a wrapper or a runtime logger handle.
+- The current record fields are `level : Level`, `timestamp_ms : UInt64`, `target : String`, `message : String`, and `fields : Array[Field]`.
+- `Record` is the common value passed through `Logger`, `AsyncLogger`, sink callbacks, formatters, predicates, and patch helpers.
+- Direct construction usually starts with `Record::new(...)`, while logger write APIs create records for you during normal logging.
+
+### How to Use
+
+Here are some specific examples provided.
+
+#### When Need A Shared Event Shape For Low-level Integrations
+
+When custom formatter or sink code should work with the same event model as the logger runtime:
+```moonbit
+let callback = fn(rec : Record) {
+  println(format_json(rec))
+}
+```
+
+In this example, the alias makes it explicit that the callback receives the public record type used everywhere else in the API.
+
+#### When Need To Inspect Record Data Directly
+
+When filters, tests, or adapters should read event fields without going through string output:
+```moonbit
+let rec = Record::new(Level::Info, "started", target="svc")
+println(rec.target)
+```
+
+In this example, the caller reads the structured event data directly instead of reparsing formatted output.
+
+### Error Case
+
+e.g.:
+- `Record` itself does not have a runtime failure mode.
+
+- Empty `target` or empty `fields` are valid and are represented directly in the record value.
+
+### Notes
+
+1. Use `Record::new(...)` when a record should be created explicitly outside normal logger write APIs.
+
+2. This alias is the shared event contract for sync logging, async logging, filtering, patching, and formatting.