📝 Fix policy test and doc

docs/api/configured-logger-file-policy-or-none.md

@@ -0,0 +1,79 @@
+---
+name: configured-logger-file-policy-or-none
+group: api
+category: runtime
+update-time: 20260707
+description: Read the current runtime file policy from a ConfiguredLogger only when it is actually file-backed.
+key-word:
+    - logger
+    - runtime
+    - file
+    - truthful
+---
+
+## Configured-logger-file-policy-or-none
+
+Read the current runtime file policy from a `ConfiguredLogger` only when it is actually file-backed.
+
+This is the truthful companion to `file_policy()`. Prefer it for diagnostics and recovery logic that must avoid fallback policy objects.
+
+### Interface
+
+```moonbit
+pub fn ConfiguredLogger::file_policy_or_none(self : ConfiguredLogger) -> FileSinkPolicy? {}
+```
+
+#### input
+
+- `self : ConfiguredLogger` - Config-driven runtime logger whose current file policy should be inspected.
+
+#### output
+
+- `FileSinkPolicy?` - `Some(policy)` when the configured sink is file-backed, otherwise `None`.
+
+### Explanation
+
+Detailed rules explaining key parameters and behaviors
+
+- File-backed sinks return `Some(current_policy)` through the wrapped `RuntimeSink`.
+- Queued file sinks forward the wrapped inner file sink policy as `Some(current_policy)`.
+- Non-file sinks return `None`.
+- This helper is broader than `file_append_mode()` or `file_auto_flush()` because it returns the whole policy object without fallback synthesis.
+
+### How to Use
+
+Here are some specific examples provided.
+
+#### When Need Truthful Policy Diagnostics
+
+When diagnostics should inspect file policy only if file semantics exist:
+```moonbit
+match logger.file_policy_or_none() {
+  Some(policy) => ignore(policy)
+  None => ()
+}
+```
+
+In this example, `None` means there is no real file policy to inspect.
+
+#### When Need Compatibility-free Recovery Decisions
+
+When recovery logic should not treat a fallback object as real state:
+```moonbit
+let maybe_policy = logger.file_policy_or_none()
+```
+
+In this example, callers can distinguish missing file semantics from a live policy snapshot.
+
+### Error Case
+
+e.g.:
+- If the configured sink is not file-backed, the method returns `None`.
+
+- If callers need default-policy comparison, pair it with `file_default_policy_or_none()`.
+
+### Notes
+
+1. Prefer this helper over `file_policy()` for truthful runtime diagnostics.
+
+2. `file_policy()` remains available as the compatibility fallback API.