fix: add --enable-unsafe-swiftshader to e2e test for CI WebGL support

The headless CI environment fails to create valid WebGL framebuffers,
causing PixiJS pixel reads to fail silently and GIF export to hang.
SwiftShader provides a software WebGL implementation that works reliably.

tests/e2e/gif-export.spec.ts

@@ -18,6 +18,8 @@ test("exports a GIF from a loaded video", async () => {
 			MAIN_JS,
 			// Required in CI sandbox environments (GitHub Actions, Docker, etc.)
 			"--no-sandbox",
+			// Force software WebGL in headless CI to avoid GPU framebuffer errors.
+			"--enable-unsafe-swiftshader",
 		],
 		env: {
 			...process.env,