Scene Manager: fixes from the first run against a real Libreflow

- Update / version switch: Blender 5.2 replaces the library on reload
  (renamed after its file, custom properties gone); find it by path and
  restore its name and tags.
- Remove the libraries an asset linked indirectly when it is removed or
  fails to load (remove_unused_libraries), never a managed one.
- Config: real Kitsu asset types for link modes and Shot Viewer groups,
  setdress_low files for bg_location, "environments" collection fallback.
- Dev fake server and test use the real asset types; rock links a node
  group from the essentials to cover the indirect library cleanup.
- README and CLAUDE.md updated with the live findings.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

scene_manager/library.py

@@ -135,6 +135,7 @@ def link_asset(asset, revision, context_oid):
                 f"{len(roots)} top-level collections in the file ({', '.join(c.name for c in roots)})"
             )
             bpy.data.libraries.remove(library)
+            remove_unused_libraries()
             raise LoadError(message)
         chosen = roots[0].name
 
@@ -177,14 +178,25 @@ def update(library_name, revision):
     """Point a library to another revision of its file and reload it."""
     library = bpy.data.libraries[library_name]
     path = _revision_path(revision, library.get("wtd_asset_name", library_name))
+    tags = dict(library)
     library.filepath = path
     library.reload()
-    # The reload replaces the linked data: look the library up again.
-    library = bpy.data.libraries[library_name]
+    # The reload replaces the library (named after its file, no custom properties):
+    # find it by its path, then give it back its name and tags.
+    library = next((lib for lib in bpy.data.libraries if _same_path(lib.filepath, path)), None)
+    if library is None:
+        raise LoadError(f"{library_name}: {os.path.basename(path)} could not be reloaded")
+    library.name = library_name
+    for key, value in tags.items():
+        library[key] = value
     library["wtd_revision"] = revision["name"]
     return library
 
 
+def _same_path(a, b):
+    return os.path.normcase(os.path.normpath(bpy.path.abspath(a))) == os.path.normcase(os.path.normpath(b))
+
+
 def remove_instance(instance):
     if isinstance(instance, bpy.types.Object):
         bpy.data.objects.remove(instance)
@@ -204,6 +216,23 @@ def remove_library(library):
     for instance in instances(library):
         remove_instance(instance)
     bpy.data.libraries.remove(library)
+    remove_unused_libraries()
+
+
+def remove_unused_libraries():
+    """Remove the libraries none of whose data is used any more, e.g. the ones a removed
+    asset linked indirectly (node group assets...). Managed libraries are kept."""
+    while True:
+        used = {
+            id.library.name
+            for id in bpy.data.user_map()
+            if id.library is not None and (id.users or id.use_fake_user)
+        }
+        unused = [lib for lib in bpy.data.libraries if lib.name not in used and not lib.get(ASSET_OID)]
+        if not unused:
+            return
+        for lib in unused:
+            bpy.data.libraries.remove(lib)
 
 
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