test(cli): keep the cli test suite off the operator's ambient QWEN_HOME (#13332)

The verification gate runs the cli suite with the runner's real HOME and
no QWEN_HOME, so the fail-closed operator-settings read in
execution-sandbox-settings.ts hit the runner's real
~/.qwen/settings.json. That file holds invalid JSON on the shared autofix
runners, and 20 test files (455 tests) that load settings or start a
serve stack failed with a FatalConfigError they have nothing to do with.

test-setup.ts already strips other operator-ambient state
(QWEN_RUNTIME_DIR, QWEN_REVIEW_SANDBOX, ...); pin QWEN_HOME to an empty
per-file temp directory there so the suite never reads the operator's
settings. settings.test.ts builds its resolution assertions on a mocked
os.homedir and so needs the ambient variable deleted at module scope.

packages/cli/src/config/settings.test.ts

@@ -95,6 +95,12 @@ vi.mock('@qwen-code/qwen-code-core', async (importOriginal) => {
   };
 });
 
+// This file's settings resolution is built on the mocked `os.homedir`, so
+// the ambient `QWEN_HOME` must not redirect it: test-setup.ts pins the
+// variable to an empty directory to keep the suite off the operator's real
+// settings. Tests that exercise `QWEN_HOME` itself set it in-body.
+delete process.env['QWEN_HOME'];
+
 // Resolve the (mocked) user-settings path once at module load. Tests mock
 // `os.homedir`, so the value is stable across the suite. Production callers
 // must keep going through `getUserSettingsPath()` to pick up `QWEN_HOME`

packages/cli/test-setup.ts

@@ -49,6 +49,21 @@ delete process.env['QWEN_RUNTIME_DIR'];
 // one explicitly.
 delete process.env['QWEN_SERVE_MAX_WORKSPACES'];
 
+// The operator's home directory is ambient state too, and the operator
+// settings read (config/execution-sandbox-settings.ts) fails CLOSED on a
+// malformed `~/.qwen/settings.json`: on a machine whose real user settings
+// file is corrupt — observed on the shared autofix verification runners —
+// every test that loads settings or starts a serve stack fails with a
+// FatalConfigError it has nothing to do with. Pinning QWEN_HOME to an empty
+// per-file directory keeps the suite off the operator's settings. Tests that
+// exercise QWEN_HOME resolution itself set or delete the variable in-body.
+import * as fs from 'node:fs';
+import * as os from 'node:os';
+import * as path from 'node:path';
+process.env['QWEN_HOME'] = fs.mkdtempSync(
+  path.join(os.tmpdir(), 'qwen-cli-test-home-'),
+);
+
 import { configure } from '@testing-library/react';
 
 import './src/test-utils/customMatchers.js';