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/hostinfo_linux.go

@@ -0,0 +1,93 @@
+// 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 deviceagent
+
+import (
+	"bufio"
+	"bytes"
+	"context"
+	"os"
+	"strings"
+	"time"
+)
+
+func platformString() string {
+	return "LINUX"
+}
+
+func collectOSVersion() string {
+	if data, err := os.ReadFile("/etc/os-release"); err == nil {
+		if prettyName := parseOSReleasePrettyName(data); prettyName != "" {
+			return prettyName
+		}
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	out, _ := runQuiet(ctx, "uname", "-sr")
+	return out
+}
+
+func collectHardwareUUID() string {
+	for _, path := range []string{
+		"/sys/class/dmi/id/product_uuid",
+		"/etc/machine-id",
+		"/var/lib/dbus/machine-id",
+	} {
+		if data, err := os.ReadFile(path); err == nil {
+			if s := strings.TrimSpace(string(data)); s != "" {
+				return s
+			}
+		}
+	}
+
+	return hashFallbackUUID()
+}
+
+func collectSerialNumber() string {
+	if data, err := os.ReadFile("/sys/class/dmi/id/product_serial"); err == nil {
+		return strings.TrimSpace(string(data))
+	}
+
+	return ""
+}
+
+func parseOSReleasePrettyName(data []byte) string {
+	sc := bufio.NewScanner(bytes.NewReader(data))
+	for sc.Scan() {
+		line := sc.Text()
+		if k, v, ok := splitKV(line); ok {
+			if k == "PRETTY_NAME" {
+				return v
+			}
+		}
+	}
+
+	return ""
+}
+
+func splitKV(line string) (string, string, bool) {
+	eq := strings.IndexByte(line, '=')
+	if eq <= 0 {
+		return "", "", false
+	}
+
+	k := strings.TrimSpace(line[:eq])
+	v := strings.TrimSpace(line[eq+1:])
+	v = strings.Trim(v, `"`)
+
+	return k, v, true
+}