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>

Front/vite.config.ts

@@ -219,19 +219,25 @@ function vitePluginStorageProxy(): Plugin {
 
 export const USER_OVERRIDES_KEY_RE = /^[A-Za-z0-9_][A-Za-z0-9_.\-]*$/;
 
-// The five in-scope axes — exact mirror of KNOWN_AXES in
-// src/user_overrides_io.py. Any payload key outside this allowlist is
-// silently dropped by the PUT handler (u4) so the on-disk schema cannot
-// drift from the backend pipeline (u2) contract. Foreign top-level keys
-// already on disk are preserved verbatim (see mergeUserOverrides).
+// The six in-scope axes — mirror of KNOWN_AXES in
+// src/user_overrides_io.py minus `slide_css` (known gap, IMP-45 #74 —
+// the Python side persists it for backend consumption; the Vite PUT does
+// not write it because the frontend never mutates the slide-level CSS
+// override). Any payload key outside this allowlist is silently dropped
+// by the PUT handler (u4) so the on-disk schema cannot drift from the
+// backend pipeline (u2) contract. Foreign top-level keys already on disk
+// are preserved verbatim (see mergeUserOverrides).
 // IMP-51 (#79) u2: added `image_overrides` (image_id → {x,y,w,h}
 // percent-of-slide coordinates).
+// IMP-55 (#93) u1: added `manual_section_assignment` (bool intent marker
+// — drag-drop sets true, layout apply/cancel sets false).
 export const KNOWN_USER_OVERRIDES_AXES = [
   "layout",
   "zone_geometries",
   "zone_sections",
   "frames",
   "image_overrides",
+  "manual_section_assignment",
 ] as const;
 export type KnownUserOverridesAxis = (typeof KNOWN_USER_OVERRIDES_AXES)[number];