test(overlay): pin an X11 session for Linux assembly tests

Fullscreen recreation only runs outside Hyprland and Sway, and the tests
inherited the running session's compositor variables, so they failed when run
from a Hyprland desktop.

src/main/assemblies/overlay.test.ts

@@ -157,6 +157,22 @@ function setup(t: TestContext, options: { platform?: NodeJS.Platform; visible?:
     Object.defineProperty(process, 'platform', { value: options.platform, configurable: true });
     t.after(() => Object.defineProperty(process, 'platform', { value: originalPlatform }));
   }
+  if (options.platform === 'linux') {
+    // Fullscreen recreation only runs outside Hyprland and Sway, so pin an X11
+    // session rather than inheriting the compositor the tests happen to run under.
+    for (const key of [
+      'HYPRLAND_INSTANCE_SIGNATURE',
+      'SWAYSOCK',
+      'XDG_CURRENT_DESKTOP',
+      'XDG_SESSION_DESKTOP',
+    ]) {
+      const original = process.env[key];
+      delete process.env[key];
+      t.after(() => {
+        if (original !== undefined) process.env[key] = original;
+      });
+    }
+  }
   const recorder = createRecorder();
   const state: FixtureState = {
     visible: options.visible ?? false,