test: the test suite exits on its own, without --forceExit (closes #585)

Some tests left timers running when they ended, and --forceExit hid them; both test scripts drop it. Six background test files left the background's 20-second timer running while an approval was pending; each now stubs it for the whole file. Five popup test files left a flash message's two-second timer running; they now use fake timers, and a wait on real zero-delay timeouts became jest.advanceTimersByTimeAsync(0). Two ethers timers can still run for up to 250 ms after a test ends; they stop before jest checks for open handles.

Model: opus-5-5

package.json

@@ -6,8 +6,8 @@
     "license": "GPL-3.0",
     "private": true,
     "scripts": {
-        "test": "jest --forceExit --maxWorkers=3",
-        "test:verbose": "jest --forceExit --maxWorkers=3 --verbose",
+        "test": "jest --maxWorkers=3",
+        "test:verbose": "jest --maxWorkers=3 --verbose",
         "build": "node build.js",
         "lint": "eslint . && prettier --check .",
         "fmt": "prettier --write .",