Same-named scenario of a dependent mod replaces the original

Scenarios now follow the rule files and entities already use: a mod adds
content under its own names and replaces another mod's scenario by shipping
the same file name and depending on it (later in load order wins, even across
scenes). The resource atlas reports one scenario name in mods not linked by
depends. Documented in AGENTS.md and the site docs (load order, scenarios).

src/ResourceAtlasBuilder.cs

@@ -151,6 +151,14 @@ namespace Cthangover.ResourceAtlas
                     Provide(result, "scene_file", file.Substring("scenes/".Length), mod.Id, file);
             }
 
+            foreach (var file in ModFileReader.ListFiles(provider, "scenarios", true))
+            {
+                // Scenarios are identified by file name: a mod replaces another
+                // mod's scenario by shipping the same name and depending on it.
+                if (file.EndsWith(".scenario", StringComparison.OrdinalIgnoreCase))
+                    Provide(result, "scenario", Path.GetFileNameWithoutExtension(file), mod.Id, file);
+            }
+
             foreach (var file in ModFileReader.ListFiles(provider, "locale", true))
             {
                 if (file.EndsWith(".properties", StringComparison.OrdinalIgnoreCase))