feat(knowledge): multi-query retrieval with LLM query rewrite

Add a shared structured query builder (knowledge_query.go) and switch
all generation paths to it, so retrieval queries carry task intent
(type, brand, region, keywords, key points) instead of a raw prompt.

ResolveContext now rewrites the query into multiple sub-questions via
the URL-markdown model, embeds and searches each, and merges/dedupes
candidates before rerank; falls back to parsed fallback questions when
rewrite is unavailable or returns too few. Resolve logs gain query
list, count, and rewrite stage/model for observability.

- knowledge_query.go/_test.go: BuildKnowledgeQuery + intent normalization
- knowledge_service.go: per-query embed/search loop, query rewrite, logs
- template_prompt/template_service/prompt_generate/article_imitation/
  kol_generation_worker: adopt the shared query builder
- generation_observability: richer task error logging

server/internal/tenant/app/article_imitation_service.go

@@ -469,7 +469,7 @@ func (s *ArticleImitationService) failGeneration(ctx context.Context, job articl
 	now := time.Now()
 	logCtx := articleImitationJobLogContext(job, stage, "", "failed", GenerationTaskResultFailure)
 	RecordGenerationTaskEvent(GenerationTaskEventFailure, logCtx)
-	LogGenerationTaskWarn(s.logger, "imitation generation failed", logCtx, zap.Error(genErr))
+	LogGenerationTaskWarn(s.logger, "imitation generation failed", logCtx, GenerationTaskErrorFields(genErr)...)
 	title := strings.TrimSpace(job.InitialTitle)
 	if title == "" {
 		title = articleImitationFallbackTitle
@@ -659,22 +659,18 @@ func buildImitationKnowledgeQuery(params map[string]interface{}) string {
 		return ""
 	}
 
-	parts := make([]string, 0, 8)
-	appendValue := func(value string) {
-		value = strings.TrimSpace(value)
-		if value == "" {
-			return
-		}
-		parts = append(parts, value)
+	intent := knowledgeQueryIntent{
+		TaskType:       "仿写文章",
+		Title:          extractString(params, "source_title"),
+		Topic:          firstNonEmptyText(extractString(params, "source_title"), extractString(params, "extra_requirements")),
+		BrandName:      extractString(params, "brand_name"),
+		Region:         extractString(params, "region"),
+		PrimaryKeyword: firstNonEmptyText(extractString(params, "source_title"), knowledgeQueryKeywordText(extractStringList(params["keywords"], 16))),
+		Keywords:       mergeKnowledgeQueryKeywords(params["keywords"]),
+		KeyPoints:      extractString(params, "preserve_points"),
+		Extra:          strings.Join([]string{extractString(params, "avoid_points"), extractString(params, "extra_requirements")}, "\n"),
 	}
-
-	appendValue(extractString(params, "source_title"))
-	appendValue(extractString(params, "brand_name"))
-	appendValue(extractString(params, "region"))
-	appendValue(strings.Join(extractStringList(params["keywords"], 16), "\n"))
-	appendValue(extractString(params, "extra_requirements"))
-
-	return strings.Join(parts, "\n")
+	return buildKnowledgeQueryInputText(intent)
 }
 
 func appendPromptLine(b *strings.Builder, label, value string) {