Constant USAGE

pub(crate) const USAGE: &str = "\
OA-Gateway — protocol-agnostic routing with pluggable adapters (prototype)

Usage:
  oa-gateway CONFIG

Arguments:
  CONFIG           Path to a TOML config file (required)

Options:
  -h, --help       Print this help and exit
  -V, --version    Print the version and exit

Examples:
  oa-gateway config/default.toml   OWP on ws://127.0.0.1:9000/ (no broker needed)
  oa-gateway config/asb.toml       adds a STOMP client for ActiveMQ on :61613
  oa-gateway config/dds.toml       loopback plus a rustdds participant on domain 0

Set RUST_LOG to change log filtering (default: info).
";

Operator-facing usage text for -h / --help.

Kept as a single string so --help and a missing-argument hint can point at the same wording.