fix(interp): collapse drifted boxed EvaluateGetOnRecord onto the RV implementation

[nickna]

One of the fix-first duplication findings from the 2026-07-01 audit (re-verified today): EvaluateGetOnRecord (boxed) and EvaluateGetOnRecordRV were a ~68-line near-duplicate that had already drifted — the boxed __proto__ walk stopped at a SharpTSInstance prototype and dispatched getters via legacy .Call, while the RV loop handles the instance arm and uses CallV2.

Observable bug fixed

Boxed callers are the named-CJS-import interop reads (Interpreter.cs import/re-export paths) and the for-of iterator-protocol done/value reads. With a CJS module whose exports object is Object.create(new Point()):

// point.cjs: class Point { constructor() { this.x = 42; } }
//            module.exports = Object.create(new Point());
import { x } from "./point.cjs";
console.log(x); // main: undefined  →  this PR: 42

Change

The boxed method is now a one-line .ToObject() adapter over EvaluateGetOnRecordRV (−65 lines; RuntimeValue.ToObject maps Undefined back to the SharpTSUndefined.Instance sentinel, so miss behavior is identical). Rationale docs moved onto the RV method, which is now the single implementation.

Verification

• Live before/after repro above (pre-fix binaries print undefined, post-fix 42), plus a for-of protocol sanity check
• Full unit suite: 15,452/15,452 pass
• Test262 interpreter baseline diff clean (subset incl. built-ins/Object, property-accessors — no regressions, no unexpected new-passes)
• TS-conformance unaffected (type-checker only; this is a runtime change)