Record shape-recs now compare type-aware like the table form: eq-map-pairs
returns nil for a record so equality falls to deep=, which is type-aware via the
per-type interned descriptor. A record equals only a same-type record, never a
plain map (cross-type and record-vs-map were wrongly equal under JOLT_SHAPE).
assoc of a new (undeclared) key keeps the record type and grows a slot, matching
Clojure's record-extension semantics.
Adds test/integration/record-shape-test.janet locking in the runtime record
mechanism (tag, field access, virtual :jolt/deftype, type-preserving assoc,
dissoc demotion, type-aware equality, #ns.Type{...} printing).
