✨ Add file sink reopen and failure counters

bitlogger/README.mbt.md

@@ -46,8 +46,8 @@ BitLogger 是一个基于 MoonBit 的结构化日志库。
 - 支持 `parse_logger_config_text(...)`、`stringify_logger_config(...)` 进行最小 JSON 配置读写
 - config-driven logger assembly via `build_logger(...)`
 - 支持 `build_logger(...)` 将配置组装为可直接使用的 logger
-- native-only file output via `file_sink(...)`, with basic size rotation and backup retention
-- 支持 `file_sink(...)`、基础 size rotation 与 backup retention，但当前仅保证 `native/llvm` backend 可用
+- native-only file output via `file_sink(...)`, with basic size rotation, backup retention, explicit `reopen()`, and failure counters
+- 支持 `file_sink(...)`、基础 size rotation / backup retention、显式 `reopen()` 与失败计数，但当前仅保证 `native/llvm` backend 可用
 
 ## Example / 示例
 
@@ -220,3 +220,6 @@ test {
 - basic rotation is size-based / 当前基础轮转为按文件大小触发
 - `file_rotation(max_bytes, max_backups=...)` controls threshold and retained backups / `file_rotation(max_bytes, max_backups=...)` 控制触发阈值和保留备份数
 - JSON config uses `sink.rotation.max_bytes` and `sink.rotation.max_backups` / JSON 配置使用 `sink.rotation.max_bytes` 与 `sink.rotation.max_backups`
+- `FileSink::reopen()` can explicitly reopen the current file handle / `FileSink::reopen()` 可显式重开当前文件句柄
+- `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
+- 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