feat(session-async): add /api/score/session_async with incremental session report aggregation

- New POST /api/score/session_async endpoint: same session_id calls append to one shared report
- New GET /api/score/sessions/{session_id}: returns call_count, metric_means, all job records
- New GET /api/score/session/jobs/{job_id}: individual call status
- SessionScoreJobManager: deterministic run_id from session_id, per-session mutex for CSV append, advisor regenerated on every call
- SessionScoreRequest (extends ScoreRequest + session_id), SessionScoreJobResponse, SessionStatus models added
- 24 new tests, all passing

chore(weighted-score): comment out 综合加权得分 display and computation

- report.js: hide 综合加权得分 card in report detail page
- score_jobs.js: hide 综合 chip in async job list
- report_builder.py: overall_ws=None (computation disabled)
- summary.py: weighted_score summary line disabled
- evaluator.py: weighted_score/sample_weight columns no longer written to scores.csv
- score.py /api/score: weighted_score always returns null
- score_job_manager.py + session_score_manager.py: weighted=None
- Updated 3 tests to match new behaviour (6 pre-existing failures unchanged)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

tests/test_webapp_report_builder.py

@@ -65,7 +65,8 @@ def test_build_report_uses_weighted_means_and_exposes_snapshot_weights(tmp_path:
         "faithfulness": pytest.approx(0.75, rel=1e-4),
         "context_recall": pytest.approx(0.5, rel=1e-4),
     }
-    assert report.weighted_score_mean == pytest.approx(0.6667, rel=1e-4)
+    # 综合加权得分已暂时禁用
+    assert report.weighted_score_mean is None
     assert report.metric_weights == {"faithfulness": 2.0, "context_recall": 1.0}
     assert report.doc_weights == {"a.pdf": 3.0, "b.pdf": 1.0}
     assert report.summary_markdown == "summary"