feat: make article summary prompt independent from daily digest

- Add outputs/prompts/article-summary-prompt.txt with deep knowledge
  note schema (core_conclusion, main_argument, key_methods, etc.)
- Add ArticleSummaryResult Pydantic model for the new schema
- Add validate_article_summary_payload() validator
- Add optional validator param to run_loop_payload(); defaults to
  existing validate_llm_result_payload so daily digest is unaffected
- Update article_summary.py: new prompt path, new validator, new
  Markdown output with Chinese section headers

src/summary_mcp/core/summary_loop.py

@@ -7,7 +7,7 @@ import json
 import os
 import re
 from pathlib import Path
-from typing import Any
+from typing import Any, Callable
 
 import httpx
 
@@ -183,7 +183,10 @@ def run_loop_payload(
     model: str | None,
     api_url: str | None,
     output_path: Path | None = None,
+    validator: Callable[[dict[str, Any], dict[str, Any] | None], ValidationReport] | None = None,
 ) -> tuple[int, dict[str, Any] | None, ValidationReport | None]:
+    # validator 为 None 时使用日报摘要默认校验器；传入自定义 validator 时使用传入的
+    resolved_validator = validator if validator is not None else validate_llm_result_payload
     prompt_template = load_text(prompt_path)
     if output_path is not None:
         output_path.parent.mkdir(parents=True, exist_ok=True)
@@ -223,7 +226,7 @@ def run_loop_payload(
         if output_path is not None:
             save_json(output_path, result_payload)
 
-        report = validate_llm_result_payload(result_payload, extracted_payload)
+        report = resolved_validator(result_payload, extracted_payload)
         _save_attempt_artifact(
             output_path,
             f"attempt-{attempt}.validation.json",