Records (defrecord/deftype) become shape-recs whose descriptor also carries
:type, under JOLT_SHAPE (flag off keeps the :jolt/deftype table form). A record
is a Janet tuple [descriptor field0 ...] in declared field order, so the
positional ->Name ctor maps args straight to slots.
- record-tag unifies the type accessor over both reps; instance?/satisfies?/
protocol dispatch and the . interop path go through it.
- virtual :jolt/deftype key on record shape-recs (via shape-get) keeps every
existing (get obj :jolt/deftype) dispatch site working.
- emit-kw-lookup's non-proven fallback routes any tuple to core-get (shape
aware), not gated on compile-time JOLT_SHAPE — core is baked without the flag
but still receives user shape-recs.
- assoc keeps the type (same-shape in place, new key grows a slot Clojure-style);
dissoc of a declared field demotes to a plain map; pr prints #ns.Type{...}.
- JOLT_SHAPE added to the image-cache key (it shapes core's own compiled paths).
