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/worker/assist/kol_assist_worker.go

@@ -6,7 +6,6 @@ import (
 	"errors"
 	"fmt"
 	"os"
-	"strings"
 	"time"
 
 	amqp "github.com/rabbitmq/amqp091-go"
@@ -18,8 +17,6 @@ import (
 	"github.com/geo-platform/tenant-api/internal/tenant/repository"
 )
 
-const kolAssistSystemPrompt = "You are a prompt designer for marketing content. Respond ONLY with JSON: {content: string, schema: {variables: [...]}}"
-
 var errKolAssistConsumerClosed = errors.New("kol assist consumer channel closed")
 
 type KolAssistWorker struct {
@@ -191,24 +188,21 @@ func (w *KolAssistWorker) processTask(ctx context.Context, job tenantapp.KolAssi
 		return fmt.Errorf("decode kol assist request: %w", err)
 	}
 
-	userPrompt, err := buildKolAssistUserPrompt(req)
+	generateReq, err := tenantapp.BuildKolAssistGenerateRequest(req)
 	if err != nil {
 		return err
 	}
 
-	result, err := w.llm.Generate(ctx, llm.GenerateRequest{
-		Prompt: fmt.Sprintf("SYSTEM:\n%s\n\nUSER:\n%s", kolAssistSystemPrompt, userPrompt),
-		ResponseFormat: &llm.ResponseFormat{
-			Type:        llm.ResponseFormatTypeJSONObject,
-			Name:        "kol_assist_response",
-			Description: "JSON object with content:string and schema:{variables:[]}",
-		},
-	}, nil)
+	result, err := w.llm.Generate(ctx, generateReq, nil)
 	if err != nil {
 		return fmt.Errorf("generate kol assist content: %w", err)
 	}
 
-	parsed, err := parseKolAssistResponse(result.Content)
+	parsed, err := tenantapp.ParseKolAssistResponse(result.Content)
+	if err != nil {
+		return err
+	}
+	parsed, err = tenantapp.FinalizeKolAssistResult(req, parsed)
 	if err != nil {
 		return err
 	}
@@ -223,44 +217,3 @@ func (w *KolAssistWorker) processTask(ctx context.Context, job tenantapp.KolAssi
 	}
 	return nil
 }
-
-func buildKolAssistUserPrompt(req tenantapp.AssistRequest) (string, error) {
-	switch strings.ToLower(strings.TrimSpace(req.Mode)) {
-	case "generate":
-		return req.Description, nil
-	case "optimize":
-		schemaJSON := "null"
-		if req.Schema != nil {
-			payload, err := json.Marshal(req.Schema)
-			if err != nil {
-				return "", fmt.Errorf("encode schema: %w", err)
-			}
-			schemaJSON = string(payload)
-		}
-		return fmt.Sprintf(
-			"Optimize the following prompt. Keep variable placeholders intact. Current schema: %s\n\nPROMPT:\n%s",
-			schemaJSON,
-			req.CurrentContent,
-		), nil
-	default:
-		return "", fmt.Errorf("unsupported assist mode %q", req.Mode)
-	}
-}
-
-func parseKolAssistResponse(content string) (*tenantapp.KolAssistResult, error) {
-	var result tenantapp.KolAssistResult
-	if err := json.Unmarshal([]byte(content), &result); err != nil {
-		return nil, fmt.Errorf("decode kol assist result: %w", err)
-	}
-	result.Content = strings.TrimSpace(result.Content)
-	if result.Content == "" {
-		return nil, fmt.Errorf("kol assist result content is empty")
-	}
-	if result.Schema.Variables == nil {
-		result.Schema.Variables = []tenantapp.KolVariableDefinition{}
-	}
-	if err := tenantapp.ValidateSchema(result.Schema); err != nil {
-		return nil, fmt.Errorf("invalid kol assist schema: %w", err)
-	}
-	return &result, nil
-}