📝 Add record and level API docs

docs/api/record-new.md

@@ -0,0 +1,91 @@
+---
+name: record-new
+group: api
+category: record
+update-time: 20260512
+description: Construct a log record explicitly from level, message, timestamp, target, and fields.
+key-word:
+    - record
+    - constructor
+    - logging
+    - public
+---
+
+## Record-new
+
+Construct a `Record` explicitly from its core fields. This is the low-level record constructor used beneath the logger APIs and is useful when records need to be created directly for formatting, filtering, sink callbacks, or tests.
+
+### Interface
+
+```moonbit
+pub fn Record::new(
+  level : Level,
+  message : String,
+  timestamp_ms~ : UInt64 = 0UL,
+  target~ : String = "",
+  fields~ : Array[Field] = [],
+) -> Record {}
+```
+
+#### input
+
+- `level : Level` - Severity level stored in the record.
+- `message : String` - Log message text.
+- `timestamp_ms : UInt64` - Timestamp in milliseconds, or `0UL` when omitted.
+- `target : String` - Target label for the record.
+- `fields : Array[Field]` - Structured field list attached to the record.
+
+#### output
+
+- `Record` - Structured log record value.
+
+### Explanation
+
+Detailed rules explaining key parameters and behaviors
+
+- The constructor stores the provided values directly without extra processing.
+- `timestamp_ms` defaults to `0UL`, which is the same no-timestamp convention used by loggers when timestamping is disabled.
+- `target` and `fields` are optional and may be left empty.
+- This API is useful when records need to be created outside the normal `Logger::log(...)` flow.
+
+### How to Use
+
+Here are some specific examples provided.
+
+#### When Create A Record For Formatter Tests
+
+When a formatting path should be exercised directly:
+```moonbit
+let rec = Record::new(
+  Level::Info,
+  "service started",
+  target="app",
+  fields=[field("region", "cn")],
+)
+```
+
+In this example, the record can be passed straight to `format_text(...)` or `format_json(...)`.
+
+#### When Feed A Callback Or Predicate Manually
+
+When tests or adapters work with records directly:
+```moonbit
+let rec = Record::new(Level::Warn, "retry scheduled")
+let keep = level_at_least(Level::Info)(rec)
+```
+
+In this example, the record exists independently of any logger instance.
+
+### Error Case
+
+e.g.:
+- If `target` is empty, the record remains valid and simply carries no target label.
+
+- If `fields` is empty, the record still works normally with formatters, sinks, and predicates.
+
+### Notes
+
+1. Prefer logger write APIs for normal application logging; use `Record::new(...)` when direct record construction is specifically needed.
+
+2. This constructor is especially useful in tests and low-level integrations.
+