📝 Add logger write API docs

docs/api/logger-bind.md

@@ -0,0 +1,79 @@
+---
+name: logger-bind
+group: api
+category: logging
+update-time: 20260512
+description: Attach reusable structured fields to a logger through the bind alias.
+key-word:
+    - logger
+    - bind
+    - fields
+    - public
+---
+
+## Logger-bind
+
+Attach shared structured fields to a logger through the `bind(...)` alias. This API is behaviorally identical to `with_context_fields(...)` and exists as a shorter name for common structured context binding.
+
+### Interface
+
+```moonbit
+pub fn[S] Logger::bind(self : Logger[S], fields : Array[Field]) -> Logger[ContextSink[S]] {}
+```
+
+#### input
+
+- `self : Logger[S]` - Base logger that should gain shared fields.
+- `fields : Array[Field]` - Structured fields attached to every emitted record.
+
+#### output
+
+- `Logger[ContextSink[S]]` - New logger wrapper that prepends shared fields at write time.
+
+### Explanation
+
+Detailed rules explaining key parameters and behaviors
+
+- `bind(...)` delegates directly to `with_context_fields(...)`.
+- The original logger value is not mutated; a wrapped logger is returned.
+- Shared fields are applied to every later log call emitted through the returned logger.
+- This alias is useful when you prefer shorter chaining syntax in application code.
+
+### How to Use
+
+Here are some specific examples provided.
+
+#### When Bind Shared Request Context
+
+When a logger should carry stable fields through a flow:
+```moonbit
+let request_logger = Logger::new(console_sink(), target="api")
+  .bind([field("request_id", "req-42")])
+```
+
+In this example, subsequent writes automatically include `request_id`.
+
+#### When Prefer Shorter Chaining Syntax
+
+When a context-bound child logger should stay readable:
+```moonbit
+let worker = Logger::new(console_sink(), target="app")
+  .child("worker")
+  .bind([field("component", "worker")])
+```
+
+In this example, `bind(...)` communicates intent without changing underlying behavior.
+
+### Error Case
+
+e.g.:
+- If `fields` is empty, the returned logger remains valid and simply adds no extra metadata.
+
+- If duplicate field keys are bound, all copies are preserved for downstream formatting or inspection.
+
+### Notes
+
+1. Use `bind(...)` and `with_context_fields(...)` interchangeably; choose the one that reads better in context.
+
+2. This alias exists for ergonomics, not for different semantics.
+