fix(halacha): split authority (derived) from rule_role — stop source-conflation (INV-DM7)

The extractor classified rule_type by SOURCE bindingness (higher-court→binding,
committee→persuasive) instead of by rule KIND. The gold-set proved it: 'binding'
appeared on 19/19 external rulings & 0 committees; 'persuasive' on 13/13
committees & 0 external — only 58% agreement with the human role tags. The two
axes (authority vs rule role) were crammed into one enum.

This splits them per INV-DM7:
- authority (binding/persuasive) — DERIVED from case_law.precedent_level
  (עליון/מנהלי→binding, ועדת_ערר_מחוזית→persuasive), never stored, never
  LLM-guessed. New helper halacha_quality.derive_authority; surfaced read-only
  in list_halachot / goldset_list / search results.
- rule_type — now the rule ROLE only: holding/interpretive/procedural/
  application/obiter. Both extractor prompts unified to this vocabulary;
  _coerce_halacha no longer defaults rule_type from the source; legacy
  binding→holding / persuasive→interpretive fold for safety.

UI: authority shown as a separate read-only badge (gold=מחייב / muted=משכנע)
across the review queue, precedent detail, and gold-set; the gold-set role
selector drops binding/persuasive and adds מהותי (holding).

Migration: scripts/halacha_rule_role_backfill.py re-classifies the 276 pre-split
binding/persuasive rows into a genuine role via local claude_session (run after
deploy). Gold-set correct_type/ai_correct_type 'binding'→'holding' via SQL.

Sources (≥3, per research-decision policy): OASIS LegalRuleML v1.0
(appliesAuthority/Strength as metadata orthogonal to rule logic) · SemEval-2023
Task 6 LegalEval (rhetorical roles by function, authority kept separate) ·
Bluebook signals (weight-of-authority is a separate dimension).

Invariants: ESTABLISHES INV-DM7. Upholds G1 (normalize at source — extractor
classifies role, system derives authority) and G2 (single source of truth —
authority derived, not a parallel stored field). Tests: 211 pass + new
derive_authority/coerce coverage. web-ui build + tsc clean.

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

mcp-server/tests/test_halacha_quality.py

@@ -211,23 +211,40 @@ def test_application_flag_from_rule_type():
     assert hq.FLAG_APPLICATION in flags
 
 
-def test_application_flag_from_deixis_even_if_binding():
+def test_application_flag_from_deixis_even_if_holding():
     flags = hq.compute_quality_flags(
         "במקרה דנן נדחה הערר", "כפי שקבענו במקרה דנן נדחה הערר",
-        rule_type="binding",
+        rule_type="holding",
     )
     assert hq.FLAG_APPLICATION in flags
 
 
-def test_clean_binding_rule_has_no_flags():
+def test_clean_holding_rule_has_no_flags():
     flags = hq.compute_quality_flags(
         "ועדת הערר מוסמכת לדון בטענות חוקתיות הנוגעות לתכנית",
         "הוועדה מוסמכת לדון אף בטענות מסוג זה, ככל שהן נוגעות לתכנית שבנדון.",
-        rule_type="binding",
+        rule_type="holding",
     )
     assert flags == []
 
 
+# ── INV-DM7: authority is DERIVED from the source, never a rule_type value ──
+
+def test_derive_authority_binding_for_higher_courts():
+    assert hq.derive_authority("עליון") == "binding"
+    assert hq.derive_authority("מנהלי") == "binding"
+
+
+def test_derive_authority_persuasive_for_committee():
+    assert hq.derive_authority("ועדת_ערר_מחוזית") == "persuasive"
+
+
+def test_derive_authority_none_for_unknown_or_empty():
+    assert hq.derive_authority("") is None
+    assert hq.derive_authority(None) is None
+    assert hq.derive_authority("משהו אחר") is None
+
+
 # ── #82.3 lexical near-duplicate signal ──
 
 def test_jaccard_high_for_reworded_same_rule():