test(integration): install the local extension fixture from a subdirectory (#16222)

TestRig.setup() now points QWEN_HOME at `<testDir>/.qwen-home`, and this
case installed `<testDir>` itself as the extension. An install copies its
source tree into the extension store, so the destination sat under the
source and fs.cp refused it: every E2E shard has failed on 35aa4b76 with
`Invalid src or dest: cp returned EINVAL (cannot copy ... to a subdirectory
of self ...)`.

Write the fixture into `local-extension/` and install that instead. The
case still covers install, list, update and uninstall of a local extension.

Verified against origin/main in a worktree: the case fails with the same
EINVAL before this change and passes (2/2) after it; eslint, prettier and
`tsc -p integration-tests/tsconfig.json` are clean.

integration-tests/cli/extensions-install.test.ts

@@ -22,7 +22,13 @@ const extensionUpdate = `{
 test('installs a local extension, verifies a command, and updates it', async () => {
   const rig = new TestRig();
   await rig.setup('extension install test');
-  const testServerPath = join(rig.testDir!, 'qwen-extension.json');
+  // Install from a nested directory: the rig keeps QWEN_HOME inside the test
+  // directory, and an install copies its source tree into that store, so
+  // pointing it at the test root would copy the store into itself and fs.cp
+  // rejects that with EINVAL.
+  const extensionDir = join(rig.testDir!, 'local-extension');
+  mkdirSync(extensionDir, { recursive: true });
+  const testServerPath = join(extensionDir, 'qwen-extension.json');
   writeFileSync(testServerPath, extension);
   try {
     await rig.runCommand(['extensions', 'uninstall', 'test-extension']);
@@ -30,10 +36,9 @@ test('installs a local extension, verifies a command, and updates it', async ()
     /* empty */
   }
 
-  const result = await rig.runCommand(
-    ['extensions', 'install', `${rig.testDir!}`],
-    { stdin: 'y\n' },
-  );
+  const result = await rig.runCommand(['extensions', 'install', extensionDir], {
+    stdin: 'y\n',
+  });
   expect(result).toContain('test-extension');
 
   const listResult = await rig.runCommand(['extensions', 'list']);