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/autostart_darwin_test.go

@@ -0,0 +1,87 @@
+// 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 (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestParseLoggedInUsernames(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name   string
+		output string
+		want   []string
+	}{
+		{
+			name:   "empty output",
+			output: "",
+			want:   []string{},
+		},
+		{
+			name:   "single user",
+			output: "alice\n",
+			want:   []string{"alice"},
+		},
+		{
+			name:   "multiple users",
+			output: "alice bob\n",
+			want:   []string{"alice", "bob"},
+		},
+		{
+			name:   "duplicate users",
+			output: "alice alice bob\n",
+			want:   []string{"alice", "bob"},
+		},
+		{
+			name:   "skips root and loginwindow",
+			output: "root loginwindow alice\n",
+			want:   []string{"alice"},
+		},
+		{
+			name:   "whitespace only",
+			output: "   \n",
+			want:   []string{},
+		},
+		{
+			name:   "extra whitespace between names",
+			output: "  alice   bob  \n",
+			want:   []string{"alice", "bob"},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(
+			tt.name,
+			func(t *testing.T) {
+				t.Parallel()
+
+				got := parseLoggedInUsernames(tt.output)
+				assert.Equal(t, tt.want, got)
+			},
+		)
+	}
+}