fix(resolution): merge.py レビュー指摘対応 — RED-to-GREEN テスト化＋inline 化（microsoft#3169）

@MohammadHaroonAbuomar のレビュー対応:

- 【必須】test_conditions_overlap_..._unsat_bias は同一 condition 2つで
  _condition_key 一致の早期 return を踏むだけで、main でも pass＝新ロジックを
  検証できていなかった。レビュアー提案の具体例で書き直し:
  親 deny = {and:[{x in []}, {tool eq shell}]}（_condition_unsatisfiable が
  unsatisfiable と分類するが tool==shell で子と重なる）vs 非同一の子 allow。
  → main では子 allow が生き残る（fail-open）= RED、本ブランチでは drop = GREEN
  を実機で確認済み。これにより本指摘が defense-in-depth ではなく実在の
  fail-open であることも実証。
- _condition_key 早期 return の sanity guard を別テストに分離。
- minor: _flag エイリアスを廃し ignore_left_unsatisfiable を直接渡す（grep性）。

検証: test_merge_deny.py + test_manifest_resolution.py 58 passed。
新テストは main で RED / 本ブランチで GREEN を確認。

Refs microsoft#3137

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VT2CfGX3tmPsQaofuuWwED

Author: Haruka-Kaya

agent-governance-python/agt-policies/src/agt/manifest_resolution/merge.py

@@ -257,30 +257,37 @@ def _conditions_disjoint(
     if not isinstance(left, dict) or not isinstance(right, dict):
         return False
 
-    _flag = ignore_left_unsatisfiable
     left_or = _compound_items(left, "or")
     if left_or is not None:
         return all(
-            _conditions_disjoint(item, right, ignore_left_unsatisfiable=_flag)
+            _conditions_disjoint(
+                item, right, ignore_left_unsatisfiable=ignore_left_unsatisfiable
+            )
             for item in left_or
         )
     right_or = _compound_items(right, "or")
     if right_or is not None:
         return all(
-            _conditions_disjoint(left, item, ignore_left_unsatisfiable=_flag)
+            _conditions_disjoint(
+                left, item, ignore_left_unsatisfiable=ignore_left_unsatisfiable
+            )
             for item in right_or
         )
 
     left_and = _compound_items(left, "and")
     if left_and is not None:
         return any(
-            _conditions_disjoint(item, right, ignore_left_unsatisfiable=_flag)
+            _conditions_disjoint(
+                item, right, ignore_left_unsatisfiable=ignore_left_unsatisfiable
+            )
             for item in left_and
         )
     right_and = _compound_items(right, "and")
     if right_and is not None:
         return any(
-            _conditions_disjoint(left, item, ignore_left_unsatisfiable=_flag)
+            _conditions_disjoint(
+                left, item, ignore_left_unsatisfiable=ignore_left_unsatisfiable
+            )
             for item in right_and
         )
 

agent-governance-python/agt-policies/tests/test_merge_deny.py

@@ -99,9 +99,33 @@ def test_satisfiable_compound_parent_deny_still_protects() -> None:
     assert "allow-admin" not in names
 
 
-def test_conditions_overlap_protects_parent_against_left_unsat_bias() -> None:
-    # Deny-immutability path must not declare "no overlap" by classifying the
-    # PARENT (left) condition unsatisfiable. Same field + same value overlap.
-    parent_cond = {"field": "tool", "operator": "eq", "value": "shell"}
-    child_cond = {"field": "tool", "operator": "eq", "value": "shell"}
-    assert _conditions_overlap(parent_cond, child_cond) is True
+def test_unsat_classified_parent_deny_still_protects_overlapping_child() -> None:
+    # RED on main, GREEN here. The parent deny's condition is classified
+    # unsatisfiable by `_condition_unsatisfiable` (the empty-`in` conjunct),
+    # yet it still overlaps the child via its other conjunct (`tool == shell`).
+    # On main, `_conditions_disjoint` short-circuits on the parent's
+    # unsatisfiability, declares the deny disjoint, and the child allow
+    # survives — neutralising the parent deny (fail-open, ADR-0014). The fix
+    # ignores the parent's unsatisfiability on the deny path, so the overlap is
+    # detected and the child allow is dropped.
+    parent = _doc([{
+        "name": "deny-shell", "action": "deny",
+        "condition": {"and": [
+            {"field": "x", "operator": "in", "value": []},
+            {"field": "tool", "operator": "eq", "value": "shell"},
+        ]},
+    }])
+    child = _doc([{
+        "name": "allow-shell", "action": "allow", "priority": 100,
+        "condition": {"field": "tool", "operator": "eq", "value": "shell"},
+    }])
+    names = [r["name"] for r in merge_documents([parent, child])]
+    assert "deny-shell" in names
+    assert "allow-shell" not in names
+
+
+def test_conditions_overlap_identical_conditions() -> None:
+    # Sanity guard for the `_condition_key` fast-path (non-identical-dict cases
+    # are covered by the merge_documents tests above).
+    cond = {"field": "tool", "operator": "eq", "value": "shell"}
+    assert _conditions_overlap(dict(cond), dict(cond)) is True