📝 Add global logger API docs

docs/api/set-default-min-level.md

@@ -0,0 +1,76 @@
+---
+name: set-default-min-level
+group: api
+category: global
+update-time: 20260512
+description: Update the minimum level used by the shared default logger helpers.
+key-word:
+    - global
+    - level
+    - default
+    - public
+---
+
+## Set-default-min-level
+
+Update the minimum level used by the shared default logger returned by `default_logger()` and consumed by the global `log(...)`, `info(...)`, `warn(...)`, and similar helpers.
+
+### Interface
+
+```moonbit
+pub fn set_default_min_level(level : Level) -> Unit {}
+```
+
+#### input
+
+- `level : Level` - New minimum level for the shared default logger configuration.
+
+#### output
+
+- `Unit` - No return value. The stored default threshold is updated for later global calls.
+
+### Explanation
+
+Detailed rules explaining key parameters and behaviors
+
+- The function updates the internal `Ref[Level]` used by `default_logger()`.
+- It does not mutate any separately stored `Logger` values that were created earlier.
+- Later calls to `default_logger()` and the global logging shortcuts observe the new threshold.
+- This is the main API for adjusting process-wide default severity without building a custom logger variable.
+
+### How to Use
+
+Here are some specific examples provided.
+
+#### When Raise Global Threshold In Production
+
+When verbose logs should be suppressed process-wide:
+```moonbit
+set_default_min_level(Level::Warn)
+```
+
+In this example, later global `info(...)` calls are skipped while `warn(...)` and `error(...)` remain active.
+
+#### When Enable Temporary Debug Visibility
+
+When diagnostics should be turned on for a session:
+```moonbit
+set_default_min_level(Level::Debug)
+debug("cache probe enabled")
+```
+
+In this example, the shared global path starts accepting debug records.
+
+### Error Case
+
+e.g.:
+- If the level is set too high, lower-severity global writes are intentionally skipped.
+
+- Existing custom `Logger` instances keep their own thresholds and are not retroactively changed.
+
+### Notes
+
+1. This API only affects the shared default logger workflow.
+
+2. Prefer explicit logger instances when different subsystems need different thresholds at the same time.
+