Loops over objects get compiled

Floati's compiler now handles the shape most real page code is actually made of: looping over a list of objects and reading or updating their fields. Reading a field (like item.price) and writing one (like item.total = item.price * quantity) inside a hot loop now run on the fast path instead of dropping back to the interpreter, including when the objects come from an array (the very common items[i].field pattern). It reads and writes each field exactly as the interpreter would, and it steps back to the normal path the instant anything unusual is involved, a property with a custom getter or setter, a proxy, or a field that is not a plain value, so behaviour never changes. Reading a field this way is about a third faster and updating one in place a bit faster still in our benchmarks. This release is also heavily about trust: alongside the feature there is now a fuzzer that generates thousands of random compiled loops mixing every supported operation, plus deliberately awkward cases that force the compiler to bail out mid-loop, and checks that each one produces byte-identical results with the compiler on and off. The full engine test suite continues to pass identically with the speed-up switched on and off.