enhance: test on Windows and fix what it found (#1348)

Adds a weekly and on-demand workflow that runs the cross-compiled tests on Windows Server 2025 Core in a [dockur/windows](https://github.com/dockur/windows) QEMU VM, and fixes the Windows bugs it found in host and UNC paths, env handling, shell quoting, post-task scripts, health checks, checkout, action symlinks, step summaries, Git client certificates and docker mode from a Windows host.

Host-mode steps now emit UTF-8, `bash` falls back to Git's bash instead of the WSL launcher, the runner can run as a native Windows service, steps can keep background helpers with `RUNNER_TRACKING_ID`, and Windows arm64 binaries are released.

Fixes: https://gitea.com/gitea/runner/issues/1339
Fixes: https://gitea.com/gitea/runner/issues/637
Fixes: https://gitea.com/gitea/runner/issues/1172
Fixes: https://gitea.com/gitea/runner/issues/347
Reviewed-on: https://gitea.com/gitea/runner/pulls/1348
Reviewed-by: bircni <[email protected]>

internal/pkg/process/killer_windows_test.go

@@ -4,9 +4,6 @@
 package process
 
 import (
-	"fmt"
-	"os/exec"
-	"path/filepath"
 	"testing"
 	"time"
 
@@ -29,20 +26,18 @@ func processAlive(pid int) bool {
 }
 
 func TestKillerKillsTree(t *testing.T) {
-	pidFile := filepath.Join(t.TempDir(), "child.pid")
-
-	script := fmt.Sprintf(
-		`$c = Start-Process powershell -PassThru -ArgumentList '-NoProfile','-Command','Start-Sleep -Seconds 600'; `+
-			`Set-Content -LiteralPath %q -Value $c.Id; Start-Sleep -Seconds 600`, pidFile)
-	cmd := exec.Command("powershell.exe", "-NoProfile", "-Command", script)
+	cmd, ready := newTestProcess(t, "parent", false)
 	require.NoError(t, cmd.Start())
-	t.Cleanup(func() { _ = cmd.Process.Kill() })
 
 	killer, err := NewKiller(cmd.Process)
 	require.NoError(t, err)
-	defer killer.Close()
+	t.Cleanup(func() {
+		_ = killer.Kill()
+		_ = killer.Close()
+	})
 
-	childPID := awaitChildPID(t, pidFile)
+	childPID := ready()
+	require.True(t, processAlive(childPID), "child process should start")
 
 	require.NoError(t, killer.Kill())