Scene.set() JS lifecycle, UI sprite caching, emulator test scripts

- Add Scene.set(module) so JerryScript can switch scenes via
  require()'d {init, update, dispose} modules; wire it into
  engineUpdate() and rework overworldscene.js/init.js to the new shape.
- Fix scriptManagerExecFile() never pushing its own file's directory
  onto the require() dir stack, breaking relative require() calls from
  a top-level entry script (e.g. init.js -> ./overworldscene.js).
- Cache sprite geometry across frames for uislider/uitab/uiframe
  (dialogs/textbox/settings) and give uitextbox a per-page glyph cache
  instead of one spriteBatchBuffer call per visible character. uiconsole
  drops its alloc/free vertex buffer for a fixed-size one. uifps skips
  rebuilding its label when the text hasn't changed.
- Add PSP_OPTIMIZATION_PLAN.md and a handful of UI/spritebatch unit
  tests covering the new caching logic.
- Add Dolphin/PPSSPP emulator smoke-test scripts (+ Docker variants and
  CI jobs) for GameCube/Wii/PSP.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

types/scene/scene.d.ts

@@ -24,4 +24,37 @@ declare class Scene {
 
   /** Gets the currently active scene, or undefined if none is active. */
   static getActive(): Scene | undefined;
+
+  /**
+   * Installs a scene module as the current scene, the mechanism for
+   * switching scenes from script. Tears down whatever module a previous
+   * Scene.set() call installed (calling its dispose(), then destroying
+   * the scene it owned), then creates and activates a fresh Scene and
+   * calls the new module's init() with it active -- so init() can use
+   * `new Entity()`/etc. as usual. The module's update() (if defined) is
+   * then called once per engine frame until Scene.set() is called again.
+   *
+   * Typical usage (see require.d.ts):
+   * ```js
+   * var myScene = require('./myscene.js');
+   * Scene.set(myScene);
+   * ```
+   */
+  static set(module: SceneModule): void;
+}
+
+/**
+ * The shape a scene module's `module.exports` should have to be usable
+ * with Scene.set(). All three are optional -- a module that never moves
+ * anything, for instance, can omit update().
+ */
+interface SceneModule {
+  /** Called once, right after Scene.set() creates and activates the scene. */
+  init?(): void;
+
+  /** Called once per engine frame while this module is the active scene. */
+  update?(): void;
+
+  /** Called once when this module is replaced by another Scene.set() call. */
+  dispose?(): void;
 }