Builds on #57. Swap Value::Object's payload from Rc<BTreeMap<Value, Value>>
to Rc<Object> and migrate all call sites to the Object API.
as_object / as_object_mut keep their names but return &Object / &mut Object.
The mutable accessor handles Rc::make_mut internally, so callers no longer
do it themselves. Object grows into_value() and From<Object> for Value.
Value's serializer now delegates to Object::serialize, dropping a duplicate
non-string-key stringification path.
RVM IterationState::Object is rewritten around ObjectCursor: O(log n)
steps over a shared Rc<Object>, no eager pair snapshot. Snapshot
independence is preserved by Rc copy-on-write; setup_next_iteration
advances the cursor inline and advance() becomes a no-op for this variant.
A new iteration_state_object_is_snapshot_independent_of_source test
covers CoW against a mutated alias.
Value::Set still wraps Rc<BTreeSet<Value>>; the matching Set abstraction
and its swap ship in follow-up PRs.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Add an opaque Object type for the key→value storage backing
Value::Object. It exposes a small set of methods (get, insert, remove,
iter, iter_sorted, cursor, serde) and keeps the backing store private,
so future representations -- inline small-map, hash-backed, lazy,
arena, FFI-callback -- can plug in without touching the call sites
that name this type.
Nothing in the engine uses Object yet. Value::Object still wraps
Rc<BTreeMap<Value, Value>>; the payload swap and call-site migration
come in the next PR. Object stands on its own unit tests in the
meantime.
docs/value/object.md walks through the design, the precedents it
follows (serde_json::Map, toml::Table, simdjson DOM), and the
concrete workloads the abstraction is meant to unlock.
A matching Set abstraction follows in a separate PR.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
