feat(prompts): expand keyword guidance to long-tail search queries

Tighten the analyze prompts (runtime + recommendation platform) so the
model returns 8-10 question-style search queries (哪家好/有哪些/怎么选/
价格/排名/避坑 …) instead of generic tag words, and lift the keyword cap
in normalizeAnalyzeResult from 5 to 10 to keep them. Add tests covering
the new ten-keyword window and the question-like guidance in the seeded
analyze prompt.

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

server/internal/tenant/prompts/loader_test.go

@@ -47,6 +47,9 @@ func TestPlatformTemplateSeedsInjectPromptConfig(t *testing.T) {
 	if !strings.Contains(analyzePrompt, "推荐类文章做品牌与竞品分析") {
 		t.Fatalf("analyze_prompt_template = %q, want yaml-backed analyze prompt", analyzePrompt)
 	}
+	if !strings.Contains(analyzePrompt, "全屋定制哪家好") || !strings.Contains(analyzePrompt, "搜索查询词") {
+		t.Fatalf("analyze_prompt_template = %q, want question-like long-tail query guidance", analyzePrompt)
+	}
 	if !strings.Contains(titlePrompt, "推荐类文章生成 5 个候选标题") {
 		t.Fatalf("title_prompt_template = %q, want yaml-backed title prompt", titlePrompt)
 	}
@@ -55,6 +58,24 @@ func TestPlatformTemplateSeedsInjectPromptConfig(t *testing.T) {
 	}
 }
 
+func TestAnalyzeFallbackPromptPrefersQuestionLikeQueries(t *testing.T) {
+	SetConfigFile("")
+	t.Cleanup(func() {
+		SetConfigFile("")
+	})
+
+	prompt := AnalyzeFallbackPrompt(`{"brand_name":"测试品牌","input_params":{"keyword":"全屋定制"}}`)
+	for _, want := range []string{
+		"真实用户会直接搜索的问题型长尾词",
+		"哪家好",
+		"最多返回 6 个竞品和 10 个关键词",
+	} {
+		if !strings.Contains(prompt, want) {
+			t.Fatalf("AnalyzeFallbackPrompt() missing %q in prompt:\n%s", want, prompt)
+		}
+	}
+}
+
 func TestPromptConfigReloadsAndKeepsLastGoodVersion(t *testing.T) {
 	SetConfigFile("")
 	defaultPath := resolvePromptsConfigFile()