fix(reflect): correct return values for set/get/define/delete/extensibility

[proggeramlug]

Closes #2756
Closes #2757
Closes #2758
Closes #2760
Closes #2762

Implementation

Perry's Reflect.* helpers reported success unconditionally and Reflect.getPrototypeOf returned the target object itself. This corrects the observable return values to match Node v25, covering the ordinary (non-proxy) [[Set]]/[[Delete]]/[[DefineOwnProperty]]/extensibility semantics plus the proxy-trap return-value coercion that already had the dispatch wired.

• runtime: make Reflect.set and proxy set traps return the actual set result #2756 Reflect.set — returns the real boolean [[Set]] result: false for a non-writable existing data property or a new key on a non-extensible object; coerced set-trap result for proxies. The ordinary path is computed without throwing (unlike strict-mode assignment, test_gap_object_methods: frozen / sealed / non-extensible writes don't throw in strict mode #615) via a pre-check of recorded attrs + the OBJ_FLAG_NO_EXTEND flag.
• runtime: make Reflect.getPrototypeOf return the actual prototype #2757 Reflect.getPrototypeOf — now delegates to js_object_get_prototype_of (the same lookup Object.getPrototypeOf uses), returning the actual [[Prototype]] including null for null-prototype objects, instead of the target itself. Codegen previously short-circuited to lower_expr(target); it now calls the runtime helper. The === Class.prototype constant fold in lower_expr.rs is preserved (drizzle/effect depend on it).
• runtime: make Reflect.defineProperty return false when definition fails #2758 Reflect.defineProperty — returns false when defining a new property on a non-extensible object or redefining a non-configurable property; coerced defineProperty-trap result for proxies; true on success.
• runtime: make Reflect.deleteProperty and proxy delete traps return the actual result #2760 Reflect.deleteProperty — returns the real delete result: false for a non-configurable property (and the property is left in place); coerced deleteProperty-trap result for proxies.
• runtime: give Reflect.preventExtensions and Reflect.isExtensible Reflect-specific results and errors #2762 Reflect.preventExtensions / Reflect.isExtensible — new Reflect-specific HIR variants (ReflectIsExtensible / ReflectPreventExtensions) and runtime helpers that throw TypeError on non-object targets and return booleans (preventExtensions returns true, not the object), distinct from the Object.* helpers. Proxy preventExtensions / isExtensible traps are dispatched and their results coerced.

New reflect-support predicates (extensibility flag, own-key presence, writable/configurable attrs) were extracted into crates/perry-runtime/src/object/reflect_support.rs to keep object_ops.rs under the 2000-line lint cap. The two new #[no_mangle] entry points (js_reflect_is_extensible, js_reflect_prevent_extensions) are declared in runtime_decls/objects.rs and pinned with #[used] keepalive anchors so the auto-optimize whole-program bitcode rebuild does not dead-strip them. New HIR variants use unique stable-hash tags 12043/12044.

Validation

test-files/test_gap_reflect_2756_2762.ts is byte-identical to node --experimental-strip-types under the default auto-optimize compile:

{"protoObj":true,"protoNull":null,"def1":true,"defNonExt":false,"defNonConfig":false,"del1":true,"delNonConfig":false,"delNonConfigRemains":1,"isExtBefore":true,"prevRet":true,"isExtAfter":false,"setNonWritable":false,"setNonExt":false,"setOk":true,"setOkVal":3}
prevThrow TypeError
isExtThrow TypeError
prevThrow TypeError
isExtThrow TypeError
prevThrow TypeError
isExtThrow TypeError

• check_file_size.sh — OK (object_ops.rs back to 1987 lines)
• cargo fmt --all -- --check — clean
• cargo test --release -p perry-hir — pass (incl. expr_variant_stable_hash_tags_are_unique)
• Existing test_gap_proxy_reflect.ts — still byte-identical to Node (no regression)

Note on scope

The proxy-trap return paths above are implemented because the trap-dispatch plumbing already existed. The Object-prototype-chain identity case from #2757's example (Reflect.getPrototypeOf(Object.create(proto)) === proto) is a pre-existing Object.getPrototypeOf limitation (it returns the object for plain object-literal chains) and is out of scope here — the issue explicitly scopes itself to the Reflect.getPrototypeOf helper sharing Object.getPrototypeOf semantics, which it now does. The gap test covers getPrototypeOf({}) === Object.prototype and the null-prototype case, both of which match Node.