Fix UI camera split going stale after a scene restart

A jump cut destroys all cameras and rebuilds a fresh main, leaving the stored split pointing at dead cameras. Worse, `main.ignore()` on the old main sets the id bit that the new main reuses, so objects assigned to the UI pass get ignored by the only live pass — rendering nowhere (the "clip plays in the background" bug).

- Add `liveSplit()` which validates the stored split against the scene's live camera list and clears it when stale
- Route `ensureUiCameras`, `assignUi`, and `assignWorld` through `liveSplit()` so a stale split is dropped and the pipeline falls back to a single pass

js/visuals/UiCameras.js

@@ -55,6 +55,44 @@ export function isScreenPinned(obj) {
   );
 }
 
+/**
+ * The stored split, validated against the LIVE camera list — or null
+ * (and cleared) when it is stale.
+ *
+ * A scene restart (the jump cut — GameScene._finishJump) runs the
+ * camera manager's shutdown, which DESTROYS every camera (fx-ui
+ * included) and re-adds a single fresh main. The stored split would
+ * then point at dead cameras, and worse: a later `main.ignore()` sets
+ * the OLD main's id bit on the object, and the re-created main reuses
+ * id 1 — so an object "assigned to the UI pass" is ignored by the ONLY
+ * live pass and drawn by no camera at all. That is the jump-clip
+ * "plays in the background" bug: after leaving an effects system, the
+ * next system's clip + opaque backdrop rendered nowhere while the world
+ * stayed fully visible. A split whose cameras are no longer in the
+ * scene's list is invalid — drop it so the pipeline falls back to a
+ * single pass (depth order restores the clip's topness) and a fresh
+ * split can be created if/when one is needed.
+ *
+ * @param {object} scene Phaser scene
+ * @returns {{ main: object, ui: object } | null} the live split, or null
+ */
+function liveSplit(scene) {
+  const split = scene._fxUiCameras;
+  const cams = scene.cameras?.cameras;
+  if (
+    split &&
+    split.ui &&
+    split.main &&
+    Array.isArray(cams) &&
+    cams.includes(split.main) &&
+    cams.includes(split.ui)
+  ) {
+    return split;
+  }
+  if (split) scene._fxUiCameras = null; // stale (a restart rebuilt the cameras) — forget it
+  return null;
+}
+
 /**
  * Create (once) the fixed UI camera and partition the scene's
  * top-level objects between the two passes. Idempotent — subsequent
@@ -65,7 +103,7 @@ export function isScreenPinned(obj) {
  *   the scene has no camera plugin (defensive).
  */
 export function ensureUiCameras(scene) {
-  if (scene._fxUiCameras) return scene._fxUiCameras;
+  if (liveSplit(scene)) return scene._fxUiCameras;
   const cameras = scene.cameras;
   if (!cameras?.cameras || cameras.cameras.length === 0) return null;
 
@@ -98,7 +136,7 @@ export function ensureUiCameras(scene) {
  * @param {object} child object to attach to the UI pass
  */
 export function assignUi(scene, child) {
-  const split = scene._fxUiCameras;
+  const split = liveSplit(scene);
   if (split && child) split.main.ignore(child);
 }
 
@@ -112,6 +150,6 @@ export function assignUi(scene, child) {
  * @param {object} child object to keep on the world pass
  */
 export function assignWorld(scene, child) {
-  const split = scene._fxUiCameras;
+  const split = liveSplit(scene);
   if (split && child) split.ui.ignore(child);
 }