Constant RPC_SUBSCRIBE_PATH 

pub const RPC_SUBSCRIBE_PATH: &'static str;

Mount path for @@subscribe SSE subscriptions (docs/design/rpc-transport.md §3.4a, cratestack#390). The trailing segment is the percent-decoded op id, e.g. GET /rpc/subscribe/model.User.subscribe. Unlike RPC_UNARY_PATH this is GET-only and carries no request body — auth is header-based (same as every other HTTP RPC binding), not an upgrade-time HMAC like the WS path (§3.4).