✨ Add file rotation introspection helpers

bitlogger/BitLogger_test.mbt

@@ -202,6 +202,7 @@ test "configured logger exposes file sink observability helpers" {
         kind=SinkKind::File,
         path="config-file.log",
         auto_flush=false,
+        rotation=Some(file_rotation(64, max_backups=3)),
       ),
     ),
   )
@@ -209,6 +210,14 @@ test "configured logger exposes file sink observability helpers" {
   inspect(logger.file_path(), content="config-file.log")
   inspect(logger.file_append_mode(), content="true")
   inspect(logger.file_auto_flush(), content="false")
+  inspect(logger.file_rotation_enabled(), content="true")
+  match logger.file_rotation_config() {
+    Some(rotation) => {
+      inspect(rotation.max_bytes, content="64")
+      inspect(rotation.max_backups, content="3")
+    }
+    None => inspect(false, content="true")
+  }
   inspect(logger.file_open_failures(), content=if logger.file_available() { "0" } else { "1" })
   inspect(logger.file_write_failures(), content="0")
   inspect(logger.file_flush_failures(), content="0")
@@ -216,6 +225,17 @@ test "configured logger exposes file sink observability helpers" {
   ignore(logger.close())
 }
 
+test "configured logger reports disabled rotation when file sink has none" {
+  let logger = build_logger(
+    LoggerConfig::new(
+      sink=SinkConfig::new(kind=SinkKind::File, path="config-no-rotation.log"),
+    ),
+  )
+  inspect(logger.file_rotation_enabled(), content="false")
+  inspect(logger.file_rotation_config() is None, content="true")
+  ignore(logger.close())
+}
+
 test "configured logger can reopen built file sink" {
   let logger = build_logger(
     LoggerConfig::new(

bitlogger/BitLogger_wbtest.mbt

@@ -93,6 +93,8 @@ test "file sink availability reflects backend support" {
   inspect(sink.is_available() == native_files_supported(), content="true")
   inspect(sink.append_mode(), content="true")
   inspect(sink.auto_flush_enabled(), content="true")
+  inspect(sink.rotation_enabled(), content="false")
+  inspect(sink.rotation_config() is None, content="true")
   inspect(sink.open_failures(), content=if sink.is_available() { "0" } else { "1" })
   inspect(sink.write_failures(), content="0")
   inspect(sink.flush_failures(), content="0")
@@ -109,6 +111,15 @@ test "file sink rotation config normalizes invalid inputs" {
   let rotation = file_rotation(0, max_backups=0)
   inspect(rotation.max_bytes, content="1")
   inspect(rotation.max_backups, content="1")
+  let sink = file_sink("bitlogger-rotation-config.log", rotation=Some(rotation))
+  inspect(sink.rotation_enabled(), content="true")
+  match sink.rotation_config() {
+    Some(config) => {
+      inspect(config.max_bytes, content="1")
+      inspect(config.max_backups, content="1")
+    }
+    None => inspect(false, content="true")
+  }
 }
 
 test "file sink tracks rotation failures on unavailable backend" {

bitlogger/README.mbt.md

@@ -223,6 +223,7 @@ test {
 - `FileSink::reopen()` can explicitly reopen the current file handle / `FileSink::reopen()` 可显式重开当前文件句柄
 - `append_mode()` exposes the current append policy, and `reopen(append=...)` updates that policy for later reopen calls / `append_mode()` 可读取当前 append 策略，`reopen(append=...)` 会更新后续 reopen 复用的 append 策略
 - `path()` and `auto_flush_enabled()` expose core file sink policy state / `path()` 与 `auto_flush_enabled()` 可读取 file sink 的基础策略状态
+- `rotation_enabled()` and `rotation_config()` expose whether rotation is active and which settings are currently applied / `rotation_enabled()` 与 `rotation_config()` 可读取 rotation 是否启用及当前配置参数
 - `open_failures()`、`write_failures()`、`flush_failures()`、`rotation_failures()` expose basic sink health counters / `open_failures()`、`write_failures()`、`flush_failures()`、`rotation_failures()` 可用于观察基础 sink 健康状态
-- `ConfiguredLogger` also forwards file reopen, flush, close, append-mode, path, auto-flush, and failure-counter helpers for config-built file sinks / `ConfiguredLogger` 也会为配置生成的 file sink 转发 reopen、flush、close、append-mode、path、auto-flush 与失败计数访问器
+- `ConfiguredLogger` also forwards file reopen, flush, close, append-mode, path, auto-flush, rotation-config, and failure-counter helpers for config-built file sinks / `ConfiguredLogger` 也会为配置生成的 file sink 转发 reopen、flush、close、append-mode、path、auto-flush、rotation 配置与失败计数访问器
 - current scope is observability-first, not a full self-healing sink runtime / 当前定位仍以可观测性优先，不是完整自愈型 sink runtime

bitlogger/config.mbt

@@ -255,6 +255,22 @@ pub fn RuntimeSink::file_auto_flush(self : RuntimeSink) -> Bool {
   }
 }
 
+pub fn RuntimeSink::file_rotation_enabled(self : RuntimeSink) -> Bool {
+  match self {
+    File(sink) => sink.rotation_enabled()
+    QueuedFile(sink) => sink.sink.rotation_enabled()
+    _ => false
+  }
+}
+
+pub fn RuntimeSink::file_rotation_config(self : RuntimeSink) -> FileRotation? {
+  match self {
+    File(sink) => sink.rotation_config()
+    QueuedFile(sink) => sink.sink.rotation_config()
+    _ => None
+  }
+}
+
 pub fn RuntimeSink::file_flush(self : RuntimeSink) -> Bool {
   match self {
     File(sink) => sink.flush()
@@ -351,6 +367,14 @@ pub fn ConfiguredLogger::file_auto_flush(self : ConfiguredLogger) -> Bool {
   self.sink.file_auto_flush()
 }
 
+pub fn ConfiguredLogger::file_rotation_enabled(self : ConfiguredLogger) -> Bool {
+  self.sink.file_rotation_enabled()
+}
+
+pub fn ConfiguredLogger::file_rotation_config(self : ConfiguredLogger) -> FileRotation? {
+  self.sink.file_rotation_config()
+}
+
 pub fn ConfiguredLogger::file_flush(self : ConfiguredLogger) -> Bool {
   self.sink.file_flush()
 }

bitlogger/sinks.mbt

@@ -126,6 +126,14 @@ pub fn FileSink::auto_flush_enabled(self : FileSink) -> Bool {
   self.auto_flush
 }
 
+pub fn FileSink::rotation_enabled(self : FileSink) -> Bool {
+  self.rotation is Some(_)
+}
+
+pub fn FileSink::rotation_config(self : FileSink) -> FileRotation? {
+  self.rotation
+}
+
 pub fn FileSink::close(self : FileSink) -> Bool {
   match self.handle.val {
     None => false