Function plugin_body_cap 

pub fn plugin_body_cap(route: &Route) -> u64

The cap for plugin body phases (DW-157): the route’s limits.max_body_bytes when configured, else PLUGIN_BODY_CAP_DEFAULT. The same bound governs the request and response sides (it is the only per-route body cap in the config surface). It applies even when the limits block is dry_run — it is a buffering bound for the plugin phase, not the 413 policy.