feat(kol): add SSE streaming for prompt assist

- Extract assist runtime (prompt building, response parsing, finalize)
  from the worker into kol_assist_runtime so the sync streaming path
  and the async task path share the same logic.
- Add POST /kol/manage/assist/stream as a Server-Sent Events endpoint
  emitting start/delta/completed/error events, and wire it to a
  streamAssist helper on kolManageApi that reports ApiClientError with
  the server's error envelope.
- Stream generated content live in KolPromptEditor and KolGenerateView,
  switching KolPromptEditArea to a boolean aiBusy flag and refining the
  generator page layout.
- Add KolAssistStreamEvent to shared types.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

server/internal/tenant/transport/kol_manage_handler.go

@@ -1,9 +1,12 @@
 package transport
 
 import (
+	"context"
+	"errors"
 	"io"
 	"net/http"
 	"strconv"
+	"strings"
 
 	"github.com/gin-gonic/gin"
 
@@ -21,6 +24,17 @@ type KolManageHandler struct {
 	assets     *AssetHandler
 }
 
+type kolAssistStreamEvent struct {
+	Mode    string             `json:"mode,omitempty"`
+	Status  string             `json:"status"`
+	Delta   string             `json:"delta,omitempty"`
+	Content string             `json:"content,omitempty"`
+	Schema  *app.KolSchemaJSON `json:"schema,omitempty"`
+	Error   string             `json:"error,omitempty"`
+	Model   string             `json:"model,omitempty"`
+	Done    bool               `json:"done"`
+}
+
 func NewKolManageHandler(a *bootstrap.App, assets *AssetHandler) *KolManageHandler {
 	profileSvc := app.NewKolProfileService(a.KolProfiles).WithObjectStorage(a.ObjectStorage)
 
@@ -460,6 +474,92 @@ func (h *KolManageHandler) AssistSubmit(c *gin.Context) {
 	response.Success(c, app.KolAssistSubmitResponse{TaskID: taskID})
 }
 
+func (h *KolManageHandler) AssistStream(c *gin.Context) {
+	var req app.AssistRequest
+	if err := c.ShouldBindJSON(&req); err != nil {
+		response.Error(c, response.ErrBadRequest(40001, "invalid_params", err.Error()))
+		return
+	}
+
+	actor, ok := actorFromRequest(c)
+	if !ok {
+		return
+	}
+
+	c.Header("Content-Type", "text/event-stream")
+	c.Header("Cache-Control", "no-cache")
+	c.Header("Connection", "keep-alive")
+	c.Header("X-Accel-Buffering", "no")
+
+	flusher, ok := c.Writer.(http.Flusher)
+	if !ok {
+		response.Error(c, response.ErrInternal(50011, "stream_unsupported", "response writer does not support streaming"))
+		return
+	}
+
+	if err := writeSSE(c, "start", kolAssistStreamEvent{
+		Mode:   req.Mode,
+		Status: "generating",
+		Done:   false,
+	}); err != nil {
+		return
+	}
+	flusher.Flush()
+
+	var streamed strings.Builder
+	var streamWriteErr error
+
+	result, model, err := h.assistSvc.Run(c.Request.Context(), actor, req, func(delta string) {
+		if delta == "" || streamWriteErr != nil {
+			return
+		}
+
+		streamed.WriteString(delta)
+		if writeErr := writeSSE(c, "delta", kolAssistStreamEvent{
+			Mode:    req.Mode,
+			Status:  "generating",
+			Delta:   delta,
+			Content: streamed.String(),
+			Done:    false,
+		}); writeErr != nil {
+			streamWriteErr = writeErr
+			return
+		}
+		flusher.Flush()
+	})
+	if streamWriteErr != nil {
+		return
+	}
+	if err != nil {
+		if errors.Is(c.Request.Context().Err(), context.Canceled) || errors.Is(c.Request.Context().Err(), context.DeadlineExceeded) {
+			return
+		}
+
+		appErr := response.Normalize(err)
+		_ = writeSSE(c, "error", kolAssistStreamEvent{
+			Mode:    req.Mode,
+			Status:  "failed",
+			Content: strings.TrimSpace(streamed.String()),
+			Error:   resolveKolAssistStreamErrorMessage(appErr),
+			Done:    true,
+		})
+		flusher.Flush()
+		return
+	}
+
+	if err := writeSSE(c, "completed", kolAssistStreamEvent{
+		Mode:    req.Mode,
+		Status:  "completed",
+		Content: result.Content,
+		Schema:  &result.Schema,
+		Model:   model,
+		Done:    true,
+	}); err != nil {
+		return
+	}
+	flusher.Flush()
+}
+
 func (h *KolManageHandler) AssistGet(c *gin.Context) {
 	taskID := c.Param("id")
 	if taskID == "" {
@@ -504,3 +604,16 @@ func parseInt64Param(c *gin.Context, key, label string) (int64, bool) {
 	}
 	return id, true
 }
+
+func resolveKolAssistStreamErrorMessage(appErr *response.AppError) string {
+	if appErr == nil {
+		return "AI 处理失败，请稍后重试"
+	}
+	if detail := strings.TrimSpace(appErr.Detail); detail != "" {
+		return detail
+	}
+	if message := strings.TrimSpace(appErr.Message); message != "" {
+		return message
+	}
+	return "AI 处理失败，请稍后重试"
+}

server/internal/tenant/transport/router.go

@@ -77,6 +77,7 @@ func RegisterRoutes(app *bootstrap.App) {
 	kolManage.PUT("/prompts/:id/activate", kolManageHandler.ActivatePrompt)
 	kolManage.PUT("/prompts/:id/archive", kolManageHandler.ArchivePrompt)
 	kolManage.POST("/assist", kolManageHandler.AssistSubmit)
+	kolManage.POST("/assist/stream", kolManageHandler.AssistStream)
 	kolManage.GET("/assist/:id", kolManageHandler.AssistGet)
 
 	kolDash := protected.Group("/tenant/kol/dashboard")