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/enrollment_state_test.go

@@ -0,0 +1,108 @@
+// 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.
+
+package deviceagent
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestEnrollmentMarker(t *testing.T) {
+	t.Parallel()
+
+	t.Run(
+		"marker tracks enrollment state",
+		func(t *testing.T) {
+			t.Parallel()
+
+			dir := t.TempDir()
+			runDir := EnrollmentRunDir(dir)
+
+			enrolled, err := IsEnrolled(runDir)
+			require.NoError(t, err)
+			assert.False(t, enrolled)
+
+			require.NoError(t, MarkEnrolled(runDir))
+			enrolled, err = IsEnrolled(runDir)
+			require.NoError(t, err)
+			assert.True(t, enrolled)
+
+			markerPath := enrollmentMarkerPath(runDir)
+			assert.NotEqual(t, filepath.Join(dir, EnrollmentMarkerName), markerPath)
+
+			info, err := os.Stat(markerPath)
+			require.NoError(t, err)
+			assert.Equal(t, os.FileMode(EnrollmentMarkerMode), info.Mode().Perm())
+
+			info, err = os.Stat(runDir)
+			require.NoError(t, err)
+			assert.Equal(t, os.FileMode(EnrollmentRunDirMode), info.Mode().Perm())
+
+			require.NoError(t, ClearEnrollmentMarker(runDir))
+			enrolled, err = IsEnrolled(runDir)
+			require.NoError(t, err)
+			assert.False(t, enrolled)
+		},
+	)
+
+	t.Run(
+		"clear is idempotent",
+		func(t *testing.T) {
+			t.Parallel()
+
+			runDir := EnrollmentRunDir(t.TempDir())
+
+			require.NoError(t, ClearEnrollmentMarker(runDir))
+			enrolled, err := IsEnrolled(runDir)
+			require.NoError(t, err)
+			assert.False(t, enrolled)
+		},
+	)
+
+	t.Run(
+		"default config dir resolves run dir",
+		func(t *testing.T) {
+			t.Parallel()
+
+			assert.Equal(t, DefaultEnrollmentRunDir(), EnrollmentRunDir(""))
+		},
+	)
+
+	t.Run(
+		"non-ENOENT stat errors are not treated as unenrolled",
+		func(t *testing.T) {
+			t.Parallel()
+
+			dir := t.TempDir()
+			runDir := EnrollmentRunDir(dir)
+			require.NoError(t, os.MkdirAll(filepath.Dir(runDir), 0o755))
+			require.NoError(t, os.WriteFile(runDir, []byte("x"), 0o644))
+
+			enrolled, err := IsEnrolled(runDir)
+			assert.False(t, enrolled)
+			require.Error(t, err)
+		},
+	)
+}