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]>

act/lookpath/git_bash.go

@@ -0,0 +1,25 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package lookpath
+
+import (
+	"path/filepath"
+	"strings"
+)
+
+func lookPathWindows(file string, env map[string]string, lookup func(string, map[string]string) (string, error)) (string, error) {
+	found, err := lookup(file, env)
+	isBash := strings.EqualFold(file, "bash") || strings.EqualFold(file, "bash.exe")
+	if !isBash || err == nil && !strings.EqualFold(filepath.Base(filepath.Dir(found)), "System32") { // System32's bash is the WSL launcher, Git's bash replaces it
+		return found, err
+	}
+	if git, gitErr := lookup("git.exe", env); gitErr == nil {
+		for _, relative := range []string{"../bin/bash.exe", "../usr/bin/bash.exe", "bash.exe"} {
+			if bash, bashErr := lookup(filepath.Join(filepath.Dir(git), relative), env); bashErr == nil {
+				return bash, nil
+			}
+		}
+	}
+	return found, err
+}