B-43: M3空参考号不再视为相等，单边intercompany需锁定才可计算

src/bank_importer/db.py

@@ -507,7 +507,8 @@ MIGRATIONS: tuple[Migration, ...] = (
              ON payer.decision_id = d.id AND payer.role = 'payer'
         JOIN transfer_decision_participants payee
              ON payee.decision_id = d.id AND payee.role = 'payee'
-        WHERE e.lifecycle = 'active' AND d.classification = 'intercompany';
+        WHERE e.lifecycle = 'active' AND d.classification = 'intercompany'
+          AND (d.pairing = 'paired' OR d.locked = 1);
 
         CREATE TRIGGER canonical_transfer_events_no_delete BEFORE DELETE ON canonical_transfer_events
         BEGIN SELECT RAISE (ABORT, 'canonical_transfer_events rows are immutable'); END;

src/bank_importer/matching.py

@@ -570,6 +570,24 @@ def _mirror_level(
     return None
 
 
+def _reference_same(row: sqlite3.Row, other: sqlite3.Row) -> bool:
+    """Positive reference evidence: both sides carry one equal reference.
+
+    ``None == None`` must never count as reference agreement; only "both
+    reference numbers exist and are equal" satisfies the reference layer of the
+    M1/M3 evidence. A single-sided reference is not equality either.
+    """
+    ref_row = normalize_reference(row["reference"])
+    ref_other = normalize_reference(other["reference"])
+    return bool(ref_row and ref_other and ref_row == ref_other)
+
+
+def _reference_conflict(row: sqlite3.Row, other: sqlite3.Row) -> bool:
+    ref_row = normalize_reference(row["reference"])
+    ref_other = normalize_reference(other["reference"])
+    return bool(ref_row and ref_other and ref_row != ref_other)
+
+
 def _classify_tier(
     row: sqlite3.Row,
     other: sqlite3.Row,
@@ -582,19 +600,19 @@ def _classify_tier(
     row_date = _parse_datetime(row["transaction_at"]).date()
     other_date = _parse_datetime(other["transaction_at"]).date()
     date_diff = abs((row_date - other_date).days)
-    ref_row = normalize_reference(row["reference"])
-    ref_other = normalize_reference(other["reference"])
-    ref_conflict = bool(ref_row and ref_other and ref_row != ref_other)
-    summary_match = bool(ref_row and ref_row == ref_other) or _summary_equal(row, other)
+    ref_same = _reference_same(row, other)
+    ref_conflict = _reference_conflict(row, other)
 
     if mirror == "exact":
-        if ref_row and ref_other and ref_row == ref_other and date_diff <= 3:
+        if ref_same and date_diff <= 3:
             return "M1"
         if date_diff <= 1 and not ref_conflict:
             return "M2"
         return "R1"
-    # alias / personal-mapping mirror
-    if date_diff <= 1 and not ref_conflict and (ref_row == ref_other or _summary_equal(row, other)):
+    # alias / personal-mapping mirror: only equal references (both present) or a
+    # deterministically equal summary is positive evidence; an absent reference
+    # is not.
+    if date_diff <= 1 and not ref_conflict and (ref_same or _summary_equal(row, other)):
         return "M3"
     return "R1"
 
@@ -602,11 +620,9 @@ def _classify_tier(
 def _tier_evidence(
     row: sqlite3.Row, other: sqlite3.Row
 ) -> tuple[str | None, bool]:
-    ref_row = normalize_reference(row["reference"])
-    ref_other = normalize_reference(other["reference"])
-    if ref_row and ref_other and ref_row == ref_other:
+    if _reference_same(row, other):
         ref_match = "same"
-    elif ref_row and ref_other:
+    elif _reference_conflict(row, other):
         ref_match = "conflict"
     else:
         ref_match = None