📝 document file sink policy mutators

docs/api/file-sink-clear-rotation.md

@@ -0,0 +1,71 @@
+---
+name: file-sink-clear-rotation
+group: api
+category: sink
+update-time: 20260613
+description: Disable runtime rotation on a FileSink.
+key-word:
+    - file
+    - sink
+    - rotation
+    - public
+---
+
+## File-sink-clear-rotation
+
+Disable runtime rotation on a `FileSink`. This helper is the direct shortcut for clearing rotation policy on the concrete sink.
+
+### Interface
+
+```moonbit
+pub fn FileSink::clear_rotation(self : FileSink) -> Unit {
+```
+
+#### input
+
+- `self : FileSink` - File sink whose rotation policy should be cleared.
+
+### Explanation
+
+Detailed rules explaining key parameters and behaviors
+
+- This method removes the current rotation policy by setting it to `None`.
+- It changes stored policy only and does not reopen the file.
+- Current append and auto-flush settings are left unchanged.
+- This helper is equivalent in intent to a broader setter with `None`, but is clearer at the call site.
+
+### How to Use
+
+Here are some specific examples provided.
+
+#### When Need To Disable Rotation Explicitly
+
+When direct runtime file rotation should be turned off:
+```moonbit
+sink.clear_rotation()
+```
+
+In this example, rotation policy is removed directly from the sink.
+
+#### When Need A Clear Intent Shortcut
+
+When code should make the disable-rotation intent obvious:
+```moonbit
+sink.clear_rotation()
+ignore(sink.rotation_enabled())
+```
+
+In this example, the call site reads more clearly than using a broader policy setter.
+
+### Error Case
+
+e.g.:
+- If callers need to switch to another rotation config rather than disable rotation, `set_rotation(...)` is the better API.
+
+- This helper does not report past rotation failures; use `rotation_failures()` or `state()` for diagnostics.
+
+### Notes
+
+1. Use this helper when the desired effect is simply “rotation off”.
+
+2. It is clearer than passing `None` through a broader setter when intent matters.