Add device agent library

Provide enrollment, elevated install, posture checks, keystore, and
system-tray helpers shared by the probo-agent binary.

Signed-off-by: Ludovic Vielle <ludovic@probo.com>

pkg/deviceagent/tray/dialog_darwin.go

@@ -0,0 +1,41 @@
+// Copyright (c) 2026 Probo Inc <hello@probo.com>.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+//go:build darwin
+
+package tray
+
+import (
+	"fmt"
+	"os/exec"
+)
+
+func showAbout(version string) {
+	path, ok := osascriptPath()
+	if !ok {
+		return
+	}
+
+	script := fmt.Sprintf(
+		`display alert "Probo Device Posture Agent" message %q buttons {"OK"} default button "OK"`,
+		fmt.Sprintf("Version %s\n\nReports device posture to your Probo workspace.", version),
+	)
+	_ = exec.Command(path, "-e", script).Run()
+}