feat(analysis): דגל "לא-נותח" + ניתוח-מחדש מאחד + בדיקת-השפעה (#201)

WS2b של עיצוב-מחדש זרימת-העבודה. מאפשר ניתוח כתב-הערר לבד ואז איחוד
מסמך-עיקרי שנוסף מאוחר, בלי force-delete גורף, עם diff ליו"ר.

- SCHEMA_V49: documents.claims_extracted_at + claims_extraction_status
  (אירוע-חילוץ per-מסמך, לא נגזר מ-doc_type), + אינדקס חלקי
  idx_documents_claims_pending. idempotent (ADD COLUMN IF NOT EXISTS).
  V48 שמור ל-#357.
- claims_extractor חותם את המסמך אחרי שמירת/אי-מציאת טענות.
- db.primary_docs_not_analyzed (is_primary V47 + claims_extracted_at IS NULL)
  + mark_document_claims_extracted; _row_to_doc חושף claims_analyzed.
- reanalyze_claims (כלי-MCP): snapshot→חילוץ-מאחד רק למסמכים חדשים/לא-נותחו
  (store_claims מחליף per-source ⇒ טענות אחרות נשמרות)→aggregate force=True
  (מסלול קנוני, מוחק רק legal_arguments)→_impact_diff before↔after ליו"ר.
- workflow_status חושף primary_docs_not_analyzed + next-step.
- ספ: 02-data-model §2ג (דגל לא-נותח), 04-analysis-writing §1.3.
- 5 בדיקות-יחידה ל-_impact_diff/_snapshot (פונקציות טהורות).

Invariants:
- G1 (נרמול-במקור): claims_extracted_at נחתם בנקודת-החילוץ, claims_analyzed
  נגזר ממנו — לא תיקון-בקריאה.
- G2 (מסלול קנוני יחיד / merge-not-fork): reanalyze מרחיב את מסלול
  claims_extractor+argument_aggregator הקיים, לא forks; האיחוד דרך
  store_claims per-source; aggregate force=True מוחק רק נגזר (legal_arguments).
- INV-DM (מודל-נתונים): דגל-אירוע per-מסמך, אינדקס חלקי, מקור-אמת יחיד.
- G10 (שער-אנושי): בדיקת-ההשפעה מוצגת ליו"ר, לא מוחלת אוטומטית.
- INV-TOOL idempotency: SCHEMA_V49 idempotent; ניתוח-מחדש חוזר על מסמך
  כבר-נותח הוא refresh נקי (store_methods replace per-source).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

mcp-server/tests/test_reanalyze_impact_diff.py

@@ -0,0 +1,76 @@
+"""Unit tests for the re-analysis impact diff — WS2 / task #201.
+
+`_snapshot` + `_impact_diff` are pure functions (no DB) that produce the
+before↔after summary surfaced to the chair after a merging re-analysis. They
+must report per-party argument titles added/removed and the shift in the
+priority ("recommendation balance") mix, and set ``changed`` correctly.
+"""
+
+from __future__ import annotations
+
+from legal_mcp.tools.legal_arguments import _impact_diff, _snapshot
+
+
+def _arg(party, title, priority="substantive"):
+    return {"party": party, "argument_title": title, "priority": priority}
+
+
+def test_no_change_is_flagged_false():
+    args = [_arg("appellant", "זכות עמידה"), _arg("committee", "שיהוי")]
+    snap = _snapshot(args)
+    diff = _impact_diff(snap, snap)
+    assert diff["changed"] is False
+    assert diff["total_before"] == diff["total_after"] == 2
+    # Every party entry reports changed=False.
+    assert all(p["changed"] is False for p in diff["by_party"])
+
+
+def test_added_argument_detected():
+    before = _snapshot([_arg("appellant", "זכות עמידה")])
+    after = _snapshot([_arg("appellant", "זכות עמידה"), _arg("appellant", "תחולת תמא 38")])
+    diff = _impact_diff(before, after)
+    assert diff["changed"] is True
+    assert diff["total_before"] == 1
+    assert diff["total_after"] == 2
+    appellant = next(p for p in diff["by_party"] if p["party"] == "appellant")
+    assert appellant["added_arguments"] == ["תחולת תמא 38"]
+    assert appellant["removed_arguments"] == []
+    assert appellant["party_he"] == "עוררים"
+
+
+def test_removed_argument_detected():
+    before = _snapshot([_arg("committee", "שיהוי"), _arg("committee", "סמכות")])
+    after = _snapshot([_arg("committee", "שיהוי")])
+    diff = _impact_diff(before, after)
+    committee = next(p for p in diff["by_party"] if p["party"] == "committee")
+    assert committee["removed_arguments"] == ["סמכות"]
+    assert committee["count_before"] == 2
+    assert committee["count_after"] == 1
+    assert diff["changed"] is True
+
+
+def test_priority_mix_shift_is_a_change():
+    # Same title, but priority moved threshold -> substantive: the recommendation
+    # balance shifted, so the chair must see a change even with identical titles.
+    before = _snapshot([_arg("appellant", "סמכות", priority="threshold")])
+    after = _snapshot([_arg("appellant", "סמכות", priority="substantive")])
+    diff = _impact_diff(before, after)
+    appellant = next(p for p in diff["by_party"] if p["party"] == "appellant")
+    assert appellant["added_arguments"] == []
+    assert appellant["removed_arguments"] == []
+    assert appellant["priority_before"] == {"threshold": 1}
+    assert appellant["priority_after"] == {"substantive": 1}
+    assert appellant["changed"] is True
+    assert diff["changed"] is True
+
+
+def test_new_party_appears():
+    before = _snapshot([_arg("appellant", "זכות עמידה")])
+    after = _snapshot([_arg("appellant", "זכות עמידה"), _arg("respondent", "מענה")])
+    diff = _impact_diff(before, after)
+    parties = {p["party"] for p in diff["by_party"]}
+    assert parties == {"appellant", "respondent"}
+    respondent = next(p for p in diff["by_party"] if p["party"] == "respondent")
+    assert respondent["count_before"] == 0
+    assert respondent["count_after"] == 1
+    assert respondent["added_arguments"] == ["מענה"]