Handle CLI server stdin EPIPE on teardown

The CLI server process's stdin can emit an asynchronous 'error' during
teardown: killProcessIfRunning() writes a "shutdown" request and then
immediately end()s and kill()s the process, so on Windows the buffered
write can complete with EPIPE once the read end closes. With no listener
this became an unhandled error that faulted whichever operation was
running, causing the flaky "should restart the database and run a query"
failures in the Windows cli-integration tests (the restart command also
restarts the CLI server via cliServer.restartCliServer()).

Attach an 'error' listener to the CLI server's stdin once per process in
launchProcess(). The command outcome is still reported via stdout /
process close, so a genuine failure is not masked; only the redundant
async stream error is handled (and logged).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 90105d62-02ab-405e-9c95-10466c971814

Author: cklin

extensions/ql-vscode/src/codeql-cli/cli.ts

@@ -382,7 +382,7 @@ export class CodeQLCliServer implements Disposable {
         ]
       : [];
 
-    return spawnServer(
+    const child = spawnServer(
       codeQlPath,
       "CodeQL CLI Server",
       ["execute", "cli-server"],
@@ -392,6 +392,22 @@ export class CodeQLCliServer implements Disposable {
         /**/
       },
     );
+
+    // The CLI server's stdin can emit an asynchronous 'error' when the process
+    // is torn down. In particular, killProcessIfRunning() writes a "shutdown"
+    // request and then immediately end()s and kill()s the process, so on
+    // Windows the buffered write can fail with EPIPE once the read end closes.
+    // Without a handler this surfaces as an unhandled error that faults an
+    // unrelated in-progress operation. Handle it here (once per process, so no
+    // listener accumulates) since the command outcome is reported separately
+    // via stdout / process close.
+    child.stdin.on("error", (e) => {
+      void this.logger.log(
+        `CodeQL CLI Server stdin error (ignored): ${getErrorMessage(e)}`,
+      );
+    });
+
+    return child;
   }
 
   private async runCodeQlCliInternal(