fix(cli): guard PowerShell process queries against exited PIDs (#3571)

## Summary

`processIdentity` and `processParentPid` call `Get-CimInstance Win32_Process` to look up process metadata on Windows. When the target process has already exited, `Get-CimInstance` returns null and calling `.CreationDate.ToFileTimeUtc()` or `.ParentProcessId` on it throws `InvokeMethodOnNull`. The try/catch handles it, but PowerShell writes the error to stderr, which pollutes the test runner's output and causes spurious exit code 1 on Windows CI.

Two fixes per call site:
- Null-check the CimInstance before accessing properties (`$p = ...; if ($p) { $p.Property }`)
- `-ErrorAction SilentlyContinue` + `stdio: ["pipe", "pipe", "ignore"]` to suppress any residual stderr

Fixes the recurring `Tests on windows-latest` flake on main.

## Test plan

- [x] All 196 CLI test files pass locally
- [ ] Windows CI should no longer exit 1 from PowerShell stderr noise

— Miga

packages/cli/src/utils/orphanCleanup.ts

@@ -101,9 +101,9 @@ export function processIdentity(pid: number): string | null {
           "-NoProfile",
           "-NonInteractive",
           "-Command",
-          `(Get-CimInstance Win32_Process -Filter 'ProcessId = ${pid}').CreationDate.ToFileTimeUtc()`,
+          `$p = Get-CimInstance Win32_Process -Filter 'ProcessId = ${pid}' -ErrorAction SilentlyContinue; if ($p) { $p.CreationDate.ToFileTimeUtc() }`,
         ],
-        { encoding: "utf8", timeout: 2000 },
+        { encoding: "utf8", timeout: 2000, stdio: ["pipe", "pipe", "ignore"] },
       ).trim();
       return created ? `windows:${created}` : null;
     }
@@ -140,9 +140,9 @@ function processParentPid(pid: number): number | null {
               "-NoProfile",
               "-NonInteractive",
               "-Command",
-              `(Get-CimInstance Win32_Process -Filter 'ProcessId = ${pid}').ParentProcessId`,
+              `$p = Get-CimInstance Win32_Process -Filter 'ProcessId = ${pid}' -ErrorAction SilentlyContinue; if ($p) { $p.ParentProcessId }`,
             ],
-            { encoding: "utf8", timeout: 2000 },
+            { encoding: "utf8", timeout: 2000, stdio: ["pipe", "pipe", "ignore"] },
           )
         : execFileSync("ps", ["-o", "ppid=", "-p", String(pid)], {
             encoding: "utf8",