Struct ProfileExplanation 

pub struct ProfileExplanation {
    pub capabilities: Vec<(String, Vec<(&'static str, &'static str)>)>,
    pub blocked_by: Option<(String, FacetMismatch)>,
}

A human-readable account of what a command resolved to and, when the band rejects it, which facet said no.

The engine was write-only before this: admits answered yes/no and nothing reported the axis. Both a user asking “why was this denied” and an author debugging a resolver were left bisecting by editing facets and re-running — which is exactly how an incomplete loopback delta got mistaken for a flawed approach rather than a missing line.

Fields

capabilities: Vec<(String, Vec<(&'static str, &'static str)>)>

One entry per capability: its because and the facets it sets.

blocked_by: Option<(String, FacetMismatch)>

(level name, why it refuses) — absent when the band admits the profile.