Add per-paper summary verification and cap safeguards

- Per-paper summary batches are fact-checked against abstracts (verify ->
  revise once on major issues -> re-verify), controlled by SEBRIEF_VERIFY_ENABLED
- The paper cap never drops papers already published in this week's digest
  (--force re-runs could otherwise erase them from every digest)
- SEBRIEF_MAX_PAPERS default 40 -> 60 (observed weekly volume ~47)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/test_pipeline.py

@@ -77,9 +77,31 @@ def test_build_payload_caps_papers_and_notes_rollover(env):
     env["settings"] = env["settings"].model_copy(update={"max_papers": 3})
     payload = build_payload(WEEK, env["settings"], env["store"])
     assert len(payload.papers) == 3
+    assert [p.doi for p in payload.papers] == ["10.1/p0", "10.1/p1", "10.1/p2"]
     assert any("이월" in g for g in payload.data_gaps)
 
 
+def test_cap_never_drops_papers_already_in_this_weeks_digest(env):
+    # --force re-run: p3/p4 were published in this week's digest; the cap must drop rollover
+    # candidates (p0..p2) instead, even though they sort first.
+    env["store"].pending = [make_paper(f"10.1/p{i}") for i in range(5)]
+    env["store"].published_dois = {"10.1/p3", "10.1/p4"}
+    env["settings"] = env["settings"].model_copy(update={"max_papers": 3})
+    payload = build_payload(WEEK, env["settings"], env["store"])
+    dois = [p.doi for p in payload.papers]
+    assert "10.1/p3" in dois and "10.1/p4" in dois
+    assert len(dois) == 3 and dois == ["10.1/p0", "10.1/p3", "10.1/p4"]
+
+
+def test_cap_keeps_all_published_even_beyond_max(env):
+    env["store"].pending = [make_paper(f"10.1/p{i}") for i in range(4)]
+    env["store"].published_dois = {f"10.1/p{i}" for i in range(4)}
+    env["settings"] = env["settings"].model_copy(update={"max_papers": 2})
+    payload = build_payload(WEEK, env["settings"], env["store"])
+    assert len(payload.papers) == 4  # a published paper is never dropped
+    assert not any("이월" in g for g in payload.data_gaps)
+
+
 # -------------------------------------------------------------------------------- run_digest
 def test_run_digest_happy_path_saves_marks_and_delivers(env):
     result = run_digest(WEEK, env["settings"])