refactor: move client info handling to desktop-specific files

Move client information related functions from client_info_*.go to desktop_*.go files
to better organize platform-specific code and separate desktop functionality from
shared code.

No functional changes.

desktop_darwin.go

@@ -5,3 +5,6 @@ package ctrld
 func IsDesktopPlatform() bool {
 	return true
 }
+
+// SelfDiscover reports whether ctrld should only do self discover.
+func SelfDiscover() bool { return true }