Add Phase Z B4 source-shape-aware placement

- enable B1/B2/B4 source-shape-aware F13 placement behind env flag
- align F13 placement_trace with mapper top_bullets cardinality
- preserve canonical render output when flag is off

src/phase_z2_placement_planner.py

@@ -115,26 +115,33 @@ def _assign_region_to_sub_zone(
     frame_sub_zones: list[dict[str, Any]],
     assigned_sub_zone_ids: set[str],
 ) -> Optional[dict[str, Any]]:
-    """region 에 매칭할 sub_zone 선택 (B4 v0 narrowest-first heuristic).
+    """region 에 매칭할 sub_zone 선택.
 
-    rule (B4 v0 lock — F29 deadlock 방지) :
+    Option 1 (source_shape-aware) :
+      region.source_shape_index 보유 시 *positional 1:1* — frame_sub_zones[index] 채택.
+      accepts mismatch 또는 already assigned 시 None (rejection).
+
+    Legacy (B4 v0 narrowest-first heuristic) :
       1. not-yet-assigned 중 region.content_type 을 accepts 하는 후보 수집
       2. 후보 중 accepts list 가장 *좁은* sub_zone 우선
       3. 동률이면 declaration order (Python sort 의 stability 활용)
 
-    예 (F29) :
-      region.content_type = text_block
-        candidates = [process_column(accepts=[text,transform], size 2),
-                      product_column(accepts=[text], size 1)]
-        → product_column 선택 (narrowest)
-
-      region.content_type = transform_table (이후 호출, product_column 이미 assigned)
-        candidates = [process_column] 만
-        → process_column 선택
-
     Returns :
-      sub_zone dict 또는 None (compatible 후보 없음)
+      sub_zone dict 또는 None (compatible 후보 없음 / positional accepts mismatch)
     """
+    # Option 1 positional matching
+    if region.source_shape_index is not None:
+        if region.source_shape_index >= len(frame_sub_zones):
+            return None
+        sz = frame_sub_zones[region.source_shape_index]
+        if sz["id"] in assigned_sub_zone_ids:
+            return None
+        accepts = sz.get("accepts") or []
+        if region.content_type not in accepts:
+            return None
+        return sz
+
+    # Legacy narrowest-first
     candidates: list[dict[str, Any]] = []
     for sz in frame_sub_zones:
         if sz["id"] in assigned_sub_zone_ids: