%% Entity model — the standard's objects and how they relate (EXPLANATORY, not
%% normative: the JSON pack instance + the reference validator remain normative).
%% Source of truth for the /dev "Entity model" page SVG (app/dev/route.ts).
erDiagram
    PRODUCER ||--o{ PACK : "assembles (the agent proposes)"
    FUNDER }o--o{ PACK : "consumes — gates dispose"
    FUNDER ||--o{ DISPOSITION : issues
    DISPOSITION }o--|| PACK : "references (pack_ref)"
    PACK_SUMMARY ||--|| PACK : "renders (one page)"

    PACK ||--|| APPLICANT_ENTITY : entity
    PACK ||--|{ SECTION_INSTANCE : "sections (repeatable: ':2', ':3', …)"
    PACK ||--|| READINESS : readiness
    SECTION_INSTANCE ||--|{ FIELD : fields
    FIELD ||--|| PROVENANCE : provenance
    READINESS ||--o| ATTESTATION : attestation

    SECTION_INSTANCE }|--|| CATALOGUE_SECTION : "conforms to"
    FIELD }|--|| CATALOGUE_FIELD : "governed by"
    CATALOGUE_SECTION ||--|{ CATALOGUE_FIELD : contains
    CATALOGUE_FIELD }o--o| CODE_LIST : "value bound to"
    CATALOGUE_FIELD }o--o| REGISTRY : "names verify source"
    PROVENANCE }o--o| REGISTRY : "verified facts cite"
    FACILITY_TYPE ||--o| REQUIREMENT_PROFILE : selects
    REQUIREMENT_PROFILE }o--|{ CATALOGUE_FIELD : requires
    REQUIREMENT_PROFILE ||--o{ READINESS : "determines missing[]"

    PACK {
        string schema_version "0.4.0 — required"
        string catalogue_version "0.7.0 — required"
    }
    APPLICANT_ENTITY {
        enum legal_form "entity gate: ltd/llp/plc for readiness"
        string jurisdiction "GB default"
    }
    SECTION_INSTANCE {
        string section_id "bare first instance; ':2' onwards"
    }
    FIELD {
        string field_id
        any value "null = not provided; datatype enforced"
    }
    PROVENANCE {
        enum kind "verified | self-declared | document | not_collected"
        string source "registry id (verified)"
        date date "freshness input"
    }
    READINESS {
        enum status "oven-ready | gaps-remaining"
        enum conformance_level "L1 | L2 | L3"
        list missing "instance-qualified field ids"
    }
    ATTESTATION {
        string attested_by "name + capacity"
        date attested_at
    }
    CATALOGUE_SECTION {
        string id "13 sections"
        bool repeatable "people, guarantor, security_assets"
    }
    CATALOGUE_FIELD {
        enum tag "verify | declare | doc"
        enum datatype "11-term vocabulary, enforced"
        enum data_class "personal = UK GDPR"
    }
    CODE_LIST {
        string id "17 versioned lists"
    }
    REGISTRY {
        string id "11 registries (reference-data)"
    }
    REQUIREMENT_PROFILE {
        list required_fields
        enum readiness_mode "one_shot | continuous"
    }
    FACILITY_TYPE {
        string code "15 products"
    }