📝 Add global logger API docs

docs/api/global-error.md

@@ -0,0 +1,76 @@
+---
+name: global-error
+group: api
+category: global
+update-time: 20260512
+description: Emit an error-level record through the shared default logger shortcut.
+key-word:
+    - global
+    - error
+    - default
+    - public
+---
+
+## Global-error
+
+Emit an error-level record through the shared default logger. This is the global convenience wrapper for `log(Level::Error, ...)`.
+
+### Interface
+
+```moonbit
+pub fn error(message : String, fields~ : Array[Field] = []) -> Unit {}
+```
+
+#### input
+
+- `message : String` - Error message text.
+- `fields : Array[Field]` - Optional structured fields attached to the record.
+
+#### output
+
+- `Unit` - No return value. The record is handled through the shared default logger.
+
+### Explanation
+
+Detailed rules explaining key parameters and behaviors
+
+- This helper delegates to `default_logger().error(...)`.
+- It uses the shared console sink, default target, and current threshold configuration.
+- `Error` is the highest built-in severity in the global sync helper set.
+- This helper is useful when a small app wants a direct shared failure-reporting path.
+
+### How to Use
+
+Here are some specific examples provided.
+
+#### When Report A Global Failure Event
+
+When a small application should emit an explicit failure log:
+```moonbit
+error("worker execution failed")
+```
+
+In this example, the shared default logger emits a high-severity error record.
+
+#### When Attach Structured Error Context
+
+When an error event should include machine-readable detail:
+```moonbit
+error("dispatch failed", fields=[field("job_id", "42")])
+```
+
+In this example, the global helper still supports structured fields.
+
+### Error Case
+
+e.g.:
+- If the shared minimum level is above `Error`, the call still returns without writing, though this configuration is unusual.
+
+- If one module should not share the same sink or target policy, the global helper path may be too blunt.
+
+### Notes
+
+1. Use this helper for simple shared error reporting.
+
+2. Explicit `Logger` values are usually better once the application needs richer routing or ownership boundaries.
+