fix(detect): add stub for unsupported platforms (darwin, windows, etc.)

detect package failed to compile on non-Linux/FreeBSD/OpenBSD because
candidates() and allManagers() had no fallback. Added detect_other.go
with empty implementations.

detect/detect_other.go

@@ -0,0 +1,13 @@
+//go:build !linux && !freebsd && !openbsd
+
+package detect
+
+// candidates returns an empty list on unsupported platforms.
+func candidates() []managerFactory {
+	return nil
+}
+
+// allManagers returns an empty list on unsupported platforms.
+func allManagers() []managerFactory {
+	return nil
+}