feat(#79): IMP-51 image_overrides axis (u1~u11 backend stamp+CLI+CSS inject + frontend drag/resize+persistence + tests)

Front/vite.config.ts

@@ -219,20 +219,23 @@ function vitePluginStorageProxy(): Plugin {
 
 export const USER_OVERRIDES_KEY_RE = /^[A-Za-z0-9_][A-Za-z0-9_.\-]*$/;
 
-// The four in-scope axes — exact mirror of KNOWN_AXES in
+// 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).
+// IMP-51 (#79) u2: added `image_overrides` (image_id → {x,y,w,h}
+// percent-of-slide coordinates).
 export const KNOWN_USER_OVERRIDES_AXES = [
   "layout",
   "zone_geometries",
   "zone_sections",
   "frames",
+  "image_overrides",
 ] as const;
 export type KnownUserOverridesAxis = (typeof KNOWN_USER_OVERRIDES_AXES)[number];
 
-// 1MB cap on PUT bodies. Override files in practice are < 10KB (4 axes,
+// 1MB cap on PUT bodies. Override files in practice are < 10KB (5 axes,
 // each a small dict). The cap is a safety net against runaway client
 // loops, not a real schema constraint.
 const USER_OVERRIDES_PUT_MAX_BYTES = 1_000_000;
@@ -319,9 +322,9 @@ export function handleGetUserOverrides(
 // IMP-52 u4 — pure merge function. Mirrors src/user_overrides_io.save():
 //   • Only KNOWN_USER_OVERRIDES_AXES present in `partial` are mutated.
 //   • Axes absent from `partial` are preserved verbatim from `existing`.
-//   • Foreign top-level keys in `existing` (future axes like zone_sizes
-//     or image_overrides) are preserved verbatim — allowlist guards what
-//     the PUT writes, NOT what the file already holds.
+//   • Foreign top-level keys in `existing` (future axes like zone_sizes)
+//     are preserved verbatim — allowlist guards what the PUT writes, NOT
+//     what the file already holds.
 //   • `partial[axis] = null` is the explicit clear sentinel (remove key).
 //   • Any non-axis keys in `partial` are silently dropped (allowlist).
 export function mergeUserOverrides(