feat(#93): IMP-55 u1~u12 frontend manual section swap detection (manual_section_assignment bool axis + drag-only marker gate + dual-axis persistence + backend manual-true gate)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/phase_z2_pipeline.py

@@ -8262,8 +8262,20 @@ if __name__ == "__main__":
                         except (TypeError, ValueError):
                             continue
                 overrides_geoms = _accepted
-        # zone_sections — CLI empty → fill from file (dict[str, list[str]]).
-        if not overrides_section_assignments:
+        # zone_sections — CLI empty AND persisted manual_section_assignment is
+        # exactly True → fill from file (dict[str, list[str]]). IMP-55 (#93) u9
+        # marker gate (fail-closed) : ``manual_section_assignment`` absent /
+        # False / non-bool (string/int/list/dict) all skip the fallback so a
+        # stale ``zone_sections`` axis left on disk from a prior drag cannot
+        # smuggle ``--override-section-assignment`` into the next run after the
+        # user reset intent via layout apply/cancel (u5 / u12 write
+        # ``manual_section_assignment: false`` explicitly). CLI
+        # ``--override-section-assignment`` payloads remain authoritative
+        # (u11 truth-table) — this gate only affects the file→fallback path.
+        if (
+            not overrides_section_assignments
+            and _persisted.get("manual_section_assignment") is True
+        ):
             _file_sections = _persisted.get("zone_sections")
             if isinstance(_file_sections, dict):
                 _accepted_sec: dict[str, list[str]] = {}

src/user_overrides_io.py

@@ -5,16 +5,19 @@ auto-restores user choices without re-clicking. Source of truth = MDX-keyed
 file (stem of the MDX path), NOT ``data/runs/<run_id>/`` which mints a fresh
 run_id per ``/api/run`` invocation.
 
-Schema (6 axes; stable order; IMP-51 #79 u1 added ``image_overrides``;
-IMP-45 #74 u1 added ``slide_css``):
+Schema (7 axes; stable order; IMP-51 #79 u1 added ``image_overrides``;
+IMP-45 #74 u1 added ``slide_css``; IMP-55 #93 u1 added
+``manual_section_assignment`` as a bool intent marker so the backend can
+distinguish a user drag-drop from frontend auto-carry zone_sections):
 
     {
-      "layout":          <string|null>,
-      "zone_geometries": {<zone_id>: {"x": float, "y": float, "w": float, "h": float}},
-      "zone_sections":   {<zone_id>: [<section_id>, ...]},
-      "frames":          {<unit_id>: <template_id>},
-      "image_overrides": {<image_id>: {"x": float, "y": float, "w": float, "h": float}},
-      "slide_css":       <string|null>
+      "layout":                    <string|null>,
+      "zone_geometries":           {<zone_id>: {"x": float, "y": float, "w": float, "h": float}},
+      "zone_sections":             {<zone_id>: [<section_id>, ...]},
+      "frames":                    {<unit_id>: <template_id>},
+      "image_overrides":           {<image_id>: {"x": float, "y": float, "w": float, "h": float}},
+      "slide_css":                 <string|null>,
+      "manual_section_assignment": <bool>
     }
 
 ``image_id`` is the stable identifier emitted by the user-content image
@@ -55,10 +58,13 @@ from typing import Any, Optional
 _PKG_ROOT = Path(__file__).resolve().parent.parent
 DEFAULT_OVERRIDES_ROOT = _PKG_ROOT / "data" / "user_overrides"
 
-# The six in-scope axes (IMP-51 #79 u1 added ``image_overrides``; IMP-45
-# #74 u1 added ``slide_css``). Any other top-level key in the file is
-# preserved but ignored by callers — keeps the file forward-compatible
-# with future axes (e.g., zone_sizes) without a schema bump here.
+# The seven in-scope axes (IMP-51 #79 u1 added ``image_overrides``; IMP-45
+# #74 u1 added ``slide_css``; IMP-55 #93 u1 added
+# ``manual_section_assignment`` — bool intent marker that gates whether
+# persisted ``zone_sections`` are consumed by the backend pipeline). Any
+# other top-level key in the file is preserved but ignored by callers —
+# keeps the file forward-compatible with future axes (e.g., zone_sizes)
+# without a schema bump here.
 KNOWN_AXES: tuple[str, ...] = (
     "layout",
     "zone_geometries",
@@ -66,6 +72,7 @@ KNOWN_AXES: tuple[str, ...] = (
     "frames",
     "image_overrides",
     "slide_css",
+    "manual_section_assignment",
 )
 
 # Key validation — MDX stem must be safe for filesystem use. Allow