Install macOS helper from PKG for XPC enroll

Browser enrollment used osascript on every elevate. Ship a signed
privileged helper installed at PKG time so probo:// can enroll over
XPC with no second admin prompt. Add make install/uninstall/clean for
local PKG test loops, and show alerts only on failure.

Mirror the Go lint path for the macOS SPM package: Make
targets, root configs, and a Linux CI job. Keep checks
syntax-only so they do not need a macOS SDK. Format the
existing sources so the new gates start clean.

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

pkg/deviceagent/elevate/elevate.go

@@ -32,6 +32,12 @@ type InstallOptions struct {
 	ConfigDir string // agent config / keystore dir (--dir)
 }
 
+// UninstallOptions configures an elevated probo-agent uninstall invocation.
+type UninstallOptions struct {
+	ExePath   string
+	ConfigDir string
+}
+
 func commandError(out []byte, err error) error {
 	if err == nil {
 		return nil