📝 Add logger write API docs

docs/api/logger-is-enabled.md

@@ -0,0 +1,80 @@
+---
+name: logger-is-enabled
+group: api
+category: logging
+update-time: 20260512
+description: Check whether a logger would accept a record at a given level.
+key-word:
+    - logger
+    - level
+    - enabled
+    - public
+---
+
+## Logger-is-enabled
+
+Check whether a logger would accept a record at the given level based on its current `min_level`. This API is useful for gating expensive work before building message text or fields.
+
+### Interface
+
+```moonbit
+pub fn[S] Logger::is_enabled(self : Logger[S], level : Level) -> Bool {}
+```
+
+#### input
+
+- `self : Logger[S]` - Logger whose current minimum level should be checked.
+- `level : Level` - Candidate severity to test.
+
+#### output
+
+- `Bool` - `true` when the level is enabled by the logger's current threshold.
+
+### Explanation
+
+Detailed rules explaining key parameters and behaviors
+
+- This method delegates to `level.enabled(self.min_level)`.
+- It only checks logger-level severity gating; it does not evaluate sink filters or patch logic.
+- The result reflects the current logger value, so derived loggers with different `min_level` settings can return different answers.
+- Use it when message construction or field gathering is expensive enough to justify a pre-check.
+
+### How to Use
+
+Here are some specific examples provided.
+
+#### When Avoid Expensive Debug Preparation
+
+When debug data should only be built if needed:
+```moonbit
+if logger.is_enabled(Level::Debug) {
+  logger.debug(build_debug_snapshot())
+}
+```
+
+In this example, expensive string construction is skipped unless debug logging is enabled.
+
+#### When Inspect Effective Logger Threshold
+
+When code should branch based on current logger behavior:
+```moonbit
+if logger.is_enabled(Level::Trace) {
+  logger.trace("trace path active")
+}
+```
+
+In this example, the check mirrors the same severity gate used by `log(...)`.
+
+### Error Case
+
+e.g.:
+- If `level` is below the current minimum threshold, the method returns `false`.
+
+- A `true` result does not guarantee final sink output if later filter logic rejects the record.
+
+### Notes
+
+1. This is a cheap severity check, not a full end-to-end delivery guarantee.
+
+2. Prefer using it only when precomputing the log payload is meaningfully expensive.
+