Add probo-agent CLI and deviceagent library

Introduce the standalone device agent binary and shared library
for enrollment, posture checks, self-update, and OS service
integration. Include build targets, module deps, and release
workflow so the agent can ship independently of server changes.

Signed-off-by: Bryan Frimin <bryan@probo.com>

pkg/deviceagent/service/service_windows.go

@@ -0,0 +1,73 @@
+// Copyright (c) 2025-2026 Probo Inc <hello@getprobo.com>.
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+// OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+package service
+
+import (
+	"errors"
+	"fmt"
+	"os/exec"
+	"strings"
+)
+
+// Install registers and starts the Windows service via sc.exe.
+func Install(cfg Config) error {
+	if cfg.ExePath == "" {
+		return errors.New("executable path is required")
+	}
+	if cfg.Dir == "" {
+		return errors.New("state directory is required")
+	}
+	name := DefaultWindowsName
+
+	bin := fmt.Sprintf(`"%s" run --dir "%s"`, cfg.ExePath, cfg.Dir)
+	if out, err := exec.Command(
+		"sc.exe",
+		"create",
+		name,
+		"binPath=",
+		bin,
+		"start=",
+		"auto",
+		"DisplayName=",
+		"Probo Device Posture Agent",
+	).CombinedOutput(); err != nil {
+		return fmt.Errorf("cannot run sc.exe create: %w: %s", err, strings.TrimSpace(string(out)))
+	}
+	// Restart on failure.
+	if out, err := exec.Command(
+		"sc.exe",
+		"failure",
+		name,
+		"reset=",
+		"86400",
+		"actions=",
+		"restart/1000/restart/1000/restart/1000",
+	).CombinedOutput(); err != nil {
+		return fmt.Errorf("cannot run sc.exe failure: %w: %s", err, strings.TrimSpace(string(out)))
+	}
+	if out, err := exec.Command("sc.exe", "start", name).CombinedOutput(); err != nil {
+		return fmt.Errorf("cannot run sc.exe start: %w: %s", err, strings.TrimSpace(string(out)))
+	}
+	return nil
+}
+
+func Uninstall(cfg Config) error {
+	name := DefaultWindowsName
+	_ = exec.Command("sc.exe", "stop", name).Run()
+	if out, err := exec.Command("sc.exe", "delete", name).CombinedOutput(); err != nil {
+		return fmt.Errorf("cannot run sc.exe delete: %w: %s", err, strings.TrimSpace(string(out)))
+	}
+	return nil
+}