Implement session teardown and resource management for in-process transitions

- Introduced `teardownMountedSession` to handle cleanup of mounted versions, generated data, and mod states during transitions between the editor and launcher.
- Added `flushEditorPackageLoaded` to evict save-editor modules from `package.loaded` dynamically, ensuring a clean state for subsequent sessions.
- Implemented `Game:reset` and `Game2:reset` methods to clear session-specific fields, allowing for a fresh start when returning to the launcher.
- Enhanced `Renderer` and `TileRenderer` to release GPU resources immediately, preventing memory leaks during rapid transitions.
- Updated `MagnetTrainRide` to support OAM priority overlays and manage background rendering with new shader functionality.

This commit improves the stability and performance of the application during in-process transitions, particularly on Android.

fixes Yellow color palette for title screen

fixes #1662 #1643 #1536 and finishes fixing #1597

tests/engine/android_exit_to_launcher_test.lua

@@ -77,4 +77,26 @@ do
   check(Runtime.modRequire == nil, "Runtime.reset clears modRequire")
 end
 
+-- 4. returnToLauncher / closeEditor also clear Assets.loader (orphaned Loader)
+do
+  local Assets = require("src.render.Assets")
+  Assets.installLoader({
+    overrideOrder = function() return { { id = "x", path = "mods/x" } } end,
+    derivedPath = function() return nil end,
+  })
+  check(Assets.loader ~= nil, "Assets.loader installed for the session")
+  Assets.installLoader(nil)
+  check(Assets.loader == nil, "session teardown clears Assets.loader")
+end
+
+-- 5. Gen1 Game:reset exists so main.lua need not guess field names
+do
+  local Game = require("src.core.Game")
+  check(type(Game.reset) == "function", "Game:reset is defined for in-process return")
+  Game.mods = { stale = true }
+  Game:reset()
+  check(Game.mods == nil, "Game:reset clears session fields")
+  check(type(Game.load) == "function", "Game:reset keeps methods")
+end
+
 T.finish("android_exit_to_launcher_test")