refactor: consolidate channel send logic with context-safe handlers

Optimize channel operations by introducing reusable context-aware send functions (`send` and `sendErr`) across `wsrelay`, `handlers`, and `cliproxy`. Ensure graceful handling of canceled contexts during stream operations.

sdk/api/handlers/handlers.go

@@ -506,6 +506,32 @@ func (h *BaseAPIHandler) ExecuteStreamWithAuthManager(ctx context.Context, handl
 		bootstrapRetries := 0
 		maxBootstrapRetries := StreamingBootstrapRetries(h.Cfg)
 
+		sendErr := func(msg *interfaces.ErrorMessage) bool {
+			if ctx == nil {
+				errChan <- msg
+				return true
+			}
+			select {
+			case <-ctx.Done():
+				return false
+			case errChan <- msg:
+				return true
+			}
+		}
+
+		sendData := func(chunk []byte) bool {
+			if ctx == nil {
+				dataChan <- chunk
+				return true
+			}
+			select {
+			case <-ctx.Done():
+				return false
+			case dataChan <- chunk:
+				return true
+			}
+		}
+
 		bootstrapEligible := func(err error) bool {
 			status := statusFromError(err)
 			if status == 0 {
@@ -565,12 +591,14 @@ func (h *BaseAPIHandler) ExecuteStreamWithAuthManager(ctx context.Context, handl
 							addon = hdr.Clone()
 						}
 					}
-					errChan <- &interfaces.ErrorMessage{StatusCode: status, Error: streamErr, Addon: addon}
+					_ = sendErr(&interfaces.ErrorMessage{StatusCode: status, Error: streamErr, Addon: addon})
 					return
 				}
 				if len(chunk.Payload) > 0 {
 					sentPayload = true
-					dataChan <- cloneBytes(chunk.Payload)
+					if okSendData := sendData(cloneBytes(chunk.Payload)); !okSendData {
+						return
+					}
 				}
 			}
 		}

sdk/cliproxy/auth/conductor.go

@@ -718,6 +718,7 @@ func (m *Manager) executeStreamMixedOnce(ctx context.Context, providers []string
 		go func(streamCtx context.Context, streamAuth *Auth, streamProvider string, streamChunks <-chan cliproxyexecutor.StreamChunk) {
 			defer close(out)
 			var failed bool
+			forward := true
 			for chunk := range streamChunks {
 				if chunk.Err != nil && !failed {
 					failed = true
@@ -728,7 +729,18 @@ func (m *Manager) executeStreamMixedOnce(ctx context.Context, providers []string
 					}
 					m.MarkResult(streamCtx, Result{AuthID: streamAuth.ID, Provider: streamProvider, Model: routeModel, Success: false, Error: rerr})
 				}
-				out <- chunk
+				if !forward {
+					continue
+				}
+				if streamCtx == nil {
+					out <- chunk
+					continue
+				}
+				select {
+				case <-streamCtx.Done():
+					forward = false
+				case out <- chunk:
+				}
 			}
 			if !failed {
 				m.MarkResult(streamCtx, Result{AuthID: streamAuth.ID, Provider: streamProvider, Model: routeModel, Success: true})