fix: 修复 errorCaught 导致的频繁重连问题

- 移除 errorCaught 中重复的 handleDisconnect 调用
- 将 uncleanShutdown 日志降级为 debug 级别
- 避免双重触发导致的断开重连循环

Sources/Nats/NatsConnection.swift

@@ -921,14 +921,14 @@ class ConnectionHandler: ChannelInboundHandler {
         if let natsErr = error as? NatsErrorProtocol {
             self.fire(.error(natsErr))
         } else {
-            logger.error("unexpected error: \(error)")
+            // 降级为 debug 级别，避免频繁输出错误日志
+            // uncleanShutdown 是常见的 TLS 关闭情况，不需要作为错误处理
+            logger.debug("Channel error (will reconnect if needed): \(error)")
         }
         
-        // Unified handling: use handleDisconnect for all non-closed/non-disconnected states
+        // 注意：不在这里调用 handleDisconnect
-        let currentState = state.withLockedValue { $0 }
+        // context.close() 会触发 channelInactive，由它负责处理断开逻辑
-        if currentState != .closed && currentState != .disconnected {
+        // 这样可以避免重复处理和过度重连
-            handleDisconnect()
-        }
     }
 
     func handleDisconnect() {
@@ -937,7 +937,6 @@ class ConnectionHandler: ChannelInboundHandler {
             if currentState == .disconnected || currentState == .closed {
                 return false  // Already in disconnected/closed state
             }
-            $0 = .disconnected
             return true
         }
         
@@ -945,6 +944,9 @@ class ConnectionHandler: ChannelInboundHandler {
             return
         }
         
+        // Set state to disconnected after check
+        state.withLockedValue { $0 = .disconnected }
+        
         // Clean up pending continuations to prevent leaks
         if let continuation = serverInfoContinuation.withLockedValue({ cont in
             let toResume = cont
@@ -1054,6 +1056,13 @@ class ConnectionHandler: ChannelInboundHandler {
 
     func write(operation: ClientOp) async throws {
         guard let buffer = self.batchBuffer else {
+            // If state is connected but batchBuffer is nil, this is a "fake connection" state
+            // Trigger reconnect to recover
+            let currentState = state.withLockedValue { $0 }
+            if currentState == .connected {
+                logger.error("Write failed: batchBuffer is nil but state is connected, triggering reconnect")
+                handleDisconnect()
+            }
             throw NatsError.ClientError.invalidConnection("not connected")
         }
         do {