feat(tenant): inject brand description context into every generation path

Include the current brand description in template, custom, imitation,
and KOL article-generation prompts while bounding prompt growth.

- Add a shared brand-context builder that resolves the current brand,
  compacts long descriptions, and caps rendered output at 2000 runes.
- Snapshot a structured brand prompt context on queued tasks so old
  jobs stay reproducible and retries stay stable.
- Route brand-profile facts through the existing typed fact guard so
  founding dates and year counts get the same pre-persistence validation
  as RAG facts, with brand facts outranking conflicting RAG facts.
- Fix the KOL creator to attach the brand scope its worker consumes.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

server/internal/worker/generate/kol_brand_prompt_test.go

@@ -0,0 +1,19 @@
+package generate
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestBuildKolGenerationPromptPlacesBrandBeforeKnowledge(t *testing.T) {
+	prompt := buildKolGenerationPrompt("TASK_SENTINEL", "BRAND_SENTINEL", "KNOWLEDGE_SENTINEL")
+	markers := []string{"TASK_SENTINEL", "BRAND_SENTINEL", "KNOWLEDGE_SENTINEL"}
+	previous := -1
+	for _, marker := range markers {
+		index := strings.Index(prompt, marker)
+		if index < 0 || index <= previous {
+			t.Fatalf("buildKolGenerationPrompt() = %q, markers out of order: %#v", prompt, markers)
+		}
+		previous = index
+	}
+}

server/internal/worker/generate/kol_generation_worker.go

@@ -114,8 +114,16 @@ func (w *KolGenerationWorker) Process(ctx context.Context, task tenantapp.Claime
 		w.HandleTaskFailure(ctx, task, "task_load", err)
 		return
 	}
+	brandID, brandPromptContext, err := tenantapp.ResolveGenerationBrandPromptContext(ctx, w.pool, task.TenantID, task.ArticleID, task.InputParams)
+	if err != nil {
+		w.HandleTaskFailure(ctx, task, "brand_context_load", err)
+		return
+	}
+	task.InputParams["brand_id"] = brandID
+	brandPrompt := tenantapp.RenderBrandPromptContext(brandPromptContext)
 
 	knowledgePrompt := ""
+	var knowledgeFactConstraints []tenantapp.KnowledgeFactConstraint
 	if knowledgeGroupIDs := kolKnowledgeGroupIDs(task.InputParams["knowledge_group_ids"]); len(knowledgeGroupIDs) > 0 {
 		if w.knowledge == nil {
 			w.HandleTaskFailure(ctx, task, "knowledge_resolve", fmt.Errorf("knowledge service is not configured"))
@@ -125,7 +133,7 @@ func (w *KolGenerationWorker) Process(ctx context.Context, task tenantapp.Claime
 		knowledgeContext, err := w.knowledge.ResolveContext(
 			ctx,
 			task.TenantID,
-			int64(kolIntInput(task.InputParams, "brand_id")),
+			brandID,
 			knowledgeGroupIDs,
 			buildKolKnowledgeQuery(task.InputParams),
 		)
@@ -134,12 +142,10 @@ func (w *KolGenerationWorker) Process(ctx context.Context, task tenantapp.Claime
 			return
 		}
 		knowledgePrompt = w.knowledge.RenderPromptSection(knowledgeContext)
+		knowledgeFactConstraints = knowledgeContext.FactConstraints
 	}
 
-	prompt := renderedPrompt
-	if strings.TrimSpace(knowledgePrompt) != "" {
-		prompt = strings.TrimSpace(renderedPrompt + "\n\n" + knowledgePrompt)
-	}
+	prompt := buildKolGenerationPrompt(renderedPrompt, brandPrompt, knowledgePrompt)
 
 	articleTimeout, maxOutputTokens := w.runtimeConfig()
 	generateReq := llm.GenerateRequest{
@@ -151,7 +157,8 @@ func (w *KolGenerationWorker) Process(ctx context.Context, task tenantapp.Claime
 		generateReq.WebSearch = &llm.WebSearchOptions{Enabled: true}
 	}
 
-	result, err := w.llm.Generate(ctx, generateReq, nil)
+	knowledgeFactConstraints = tenantapp.MergeKnowledgeFactConstraints(brandPromptContext.FactConstraints, knowledgeFactConstraints)
+	result, err := tenantapp.GenerateArticleWithKnowledgeFactGuard(ctx, w.llm, generateReq, knowledgeFactConstraints, nil)
 	if err != nil {
 		w.HandleTaskFailure(ctx, task, "llm_generate", err)
 		return
@@ -263,6 +270,16 @@ func (w *KolGenerationWorker) Process(ctx context.Context, task tenantapp.Claime
 	})
 }
 
+func buildKolGenerationPrompt(renderedPrompt string, brandPrompt string, knowledgePrompt string) string {
+	sections := make([]string, 0, 3)
+	for _, section := range []string{renderedPrompt, brandPrompt, knowledgePrompt} {
+		if section = strings.TrimSpace(section); section != "" {
+			sections = append(sections, section)
+		}
+	}
+	return strings.Join(sections, "\n\n")
+}
+
 func (w *KolGenerationWorker) HandleTaskFailure(ctx context.Context, task tenantapp.ClaimedGenerationTask, stage string, taskErr error) {
 	if err := tenantapp.HandleKolGenerationTaskFailure(ctx, w.pool, w.cache, task, stage, taskErr); err != nil && w.logger != nil {
 		w.logger.Warn("kol generation task failure handling failed",