📝 Add record and level API docs

docs/api/level-label.md

@@ -0,0 +1,76 @@
+---
+name: level-label
+group: api
+category: level
+update-time: 20260512
+description: Convert a level into its uppercase display label.
+key-word:
+    - level
+    - label
+    - helper
+    - public
+---
+
+## Level-label
+
+Convert a `Level` into its uppercase display label. This helper is useful for formatting, diagnostics, and user-visible output that should mirror the built-in level names.
+
+### Interface
+
+```moonbit
+pub fn Level::label(self : Level) -> String {}
+```
+
+#### input
+
+- `self : Level` - Level value whose display label should be returned.
+
+#### output
+
+- `String` - Uppercase label such as `TRACE`, `DEBUG`, `INFO`, `WARN`, or `ERROR`.
+
+### Explanation
+
+Detailed rules explaining key parameters and behaviors
+
+- The returned strings are uppercase built-in labels.
+- This helper is intended for readable output and formatter logic.
+- It is separate from `priority()`, which is for numeric ordering.
+- The label reflects the enum variant directly and does not depend on any logger configuration.
+
+### How to Use
+
+Here are some specific examples provided.
+
+#### When Show A Level In Custom Output
+
+When a callback or formatter wants a readable label:
+```moonbit
+let label = Level::Warn.label()
+```
+
+In this example, `label` becomes `"WARN"`.
+
+#### When Build Simple Human-readable Diagnostics
+
+When direct console text should include the level name:
+```moonbit
+let rec = Record::new(Level::Error, "dispatch failed")
+println(rec.level.label())
+```
+
+In this example, the output uses the built-in uppercase severity name.
+
+### Error Case
+
+e.g.:
+- There is no failure path for valid `Level` values.
+
+- If code needs numeric ordering rather than display text, `label()` is the wrong helper.
+
+### Notes
+
+1. Use this helper for presentation and diagnostics.
+
+2. Prefer `priority()` or `enabled()` for threshold logic.
+