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")

tests/engine/cache_fs_red_migration_test.lua

@@ -57,6 +57,36 @@ eq(love.filesystem.read("assets/generated/fonts/font.png"), "font-bytes",
 eq(love.filesystem.read("data/generated/constants.lua"), "return {}",
   "post-mount probe reads red data at the un-prefixed path")
 
+-- unmountVersion peels generated overlays (LIFO) then the version folder, so
+-- a later Play/Edit on another game cannot resolve this version's files.
+do
+  local mounts = love.filesystem._mounts
+  local archives = {}
+  for _, m in ipairs(mounts) do archives[#archives + 1] = m.archive end
+  local function indexOf(name)
+    for i, a in ipairs(archives) do if a == name then return i end end
+  end
+  local dataIdx = indexOf("red/data/generated")
+  local assetsIdx = indexOf("red/assets/generated")
+  check(dataIdx and assetsIdx, "mountVersion recorded generated-tree overlays")
+  check(assetsIdx > dataIdx,
+    "assets/generated was mounted after data/generated (LIFO unmount peels it first)")
+end
+check(CacheFs.unmountVersion("red") == true, "unmountVersion(red) returns true")
+check(love.filesystem.read("assets/generated/fonts/font.png") == nil,
+  "post-unmount probe no longer sees red assets at the un-prefixed path")
+check(love.filesystem.read("data/generated/constants.lua") == nil,
+  "post-unmount probe no longer sees red data at the un-prefixed path")
+do
+  local left = {}
+  for _, m in ipairs(love.filesystem._mounts) do
+    if tostring(m.archive):find("red", 1, true) then
+      left[#left + 1] = m.archive
+    end
+  end
+  eq(#left, 0, "no red/ mounts remain after unmountVersion")
+end
+
 -- no legacy cache at all: migration is a no-op, not an error
 love.filesystem.remove("red/rom-cache.complete")
 love.filesystem.remove("red/data/generated/maps.lua")

tests/engine/launcher_session_teardown_test.lua

@@ -0,0 +1,111 @@
+-- In-process launcher session teardown: Game:reset, Renderer canvas release,
+-- Runtime/Assets/LegacyCompat cleanup, and editor package.loaded discovery flush.
+--   luajit tests/engine/launcher_session_teardown_test.lua
+
+package.path = "./?.lua;./?/init.lua;" .. package.path
+love = love or require("tests.love_stub")
+
+local T = require("tests.harness")
+local check, eq = T.check, T.eq
+
+local Runtime = require("src.mods.Runtime")
+local Assets = require("src.render.Assets")
+local LegacyCompat = require("src.mods.LegacyCompat")
+local Game = require("src.core.Game")
+local Renderer = require("src.render.Renderer")
+local StateStack = require("src.core.StateStack")
+
+-- ---- Game:reset drops instance state, keeps methods ----------------------
+do
+  StateStack:init()
+  StateStack:push({ name = "stale" })
+  Game.mods = { id = "orphan" }
+  Game.save = { money = 1 }
+  Game.network = { live = true } -- future field: must not need a whitelist
+  Game.stack = StateStack
+  Game.renderer = Renderer
+  Renderer.canvas = love.graphics.newCanvas(8, 8)
+
+  Game:reset()
+
+  check(type(Game.load) == "function", "Game:reset keeps methods")
+  check(type(Game.reset) == "function", "Game:reset keeps itself")
+  check(Game.mods == nil, "Game:reset clears mods")
+  check(Game.save == nil, "Game:reset clears save")
+  check(Game.network == nil, "Game:reset clears arbitrary future fields")
+  check(Game.stack == nil, "Game:reset clears stack reference")
+  check(Game.renderer == nil, "Game:reset clears renderer reference")
+  check(StateStack:top() == nil, "Game:reset cleared the shared StateStack")
+end
+
+-- ---- Renderer:init releases prior canvases before realloc ----------------
+do
+  local first = love.graphics.newCanvas(16, 16)
+  Renderer.canvas = first
+  Renderer.battleHUDCanvas = love.graphics.newCanvas(16, 16)
+  Renderer.worldCanvas = love.graphics.newCanvas(16, 16)
+  Renderer.uprightCanvas = love.graphics.newCanvas(16, 16)
+  Renderer:init()
+  check(first.released == true,
+    "Renderer:init Object:release()s the previous primary canvas")
+  check(Renderer.canvas ~= nil and Renderer.canvas ~= first,
+    "Renderer:init allocates a fresh primary canvas")
+  check(Renderer.canvas.released ~= true,
+    "the new primary canvas is not released")
+  -- second init also releases the one just created
+  local second = Renderer.canvas
+  Renderer:init()
+  check(second.released == true,
+    "a second Renderer:init releases the canvas from the prior init")
+end
+
+-- ---- Shared singleton teardown contract (closeEditor / returnToLauncher)
+do
+  Runtime.install({ emit = function() end }, { call = function() end }, { "e" })
+  Assets.installLoader({
+    overrideOrder = function() return {} end,
+    derivedPath = function() return nil end,
+  })
+  LegacyCompat.reports = { some_mod = { order = {} } }
+
+  -- Mirrors main.lua teardownMountedSession without mounting CacheFs.
+  require("src.core.Data"):unloadGenerated()
+  Runtime.reset()
+  Assets.installLoader(nil)
+  LegacyCompat.reset()
+
+  check(Runtime.errors == nil, "teardown clears Runtime.errors")
+  check(Assets.loader == nil, "teardown clears Assets.loader")
+  eq(next(LegacyCompat.reports), nil, "teardown clears LegacyCompat.reports")
+end
+
+-- ---- Editor package.loaded discovery flush (no panel whitelist) ---------
+do
+  love.filesystem.write("tools/save-editor/App.lua", "return {}")
+  love.filesystem.write("tools/save-editor/panels/NewPanel.lua", "return {}")
+  package.loaded["App"] = { stale = true }
+  package.loaded["NewPanel"] = { stale = true }
+  package.loaded["src.core.Data"] = package.loaded["src.core.Data"] -- keep
+
+  local function isEditorFlat(name)
+    if name:find("[./]") then return false end
+    return love.filesystem.getInfo("tools/save-editor/" .. name .. ".lua") ~= nil
+      or love.filesystem.getInfo("tools/save-editor/panels/" .. name .. ".lua") ~= nil
+  end
+  for k in pairs(package.loaded) do
+    if type(k) == "string"
+        and (k:find("save%-editor", 1, false) or isEditorFlat(k)) then
+      package.loaded[k] = nil
+    end
+  end
+
+  check(package.loaded["App"] == nil, "discovery flush drops flat App")
+  check(package.loaded["NewPanel"] == nil,
+    "discovery flush drops a new panel without a hardcoded list")
+  check(package.loaded["src.core.Data"] ~= nil,
+    "discovery flush leaves engine modules alone")
+  love.filesystem.remove("tools/save-editor/App.lua")
+  love.filesystem.remove("tools/save-editor/panels/NewPanel.lua")
+end
+
+T.finish("launcher_session_teardown_test")