[Loom] Preserve C++ increment values and conditional mutations

[benvanik]

C/C++ prefix and postfix ++/-- can now produce values from integer and pointer bindings. This admits ordinary pointer streams and conditional counters that previously failed import:

void copy(const unsigned* input, unsigned* output, unsigned count) {
  unsigned index = 0;
  while (index++ < count) {
    *output++ = *input++;
  }
}

unsigned visit(unsigned value, unsigned limit) {
  unsigned visits = 0;
  bool accepted = value < limit && visits++ == 0u;
  return visits + (unsigned)accepted;
}

Postfix expressions return the captured previous value; prefix expressions return the updated value. Updates use the existing promoted integer arithmetic and narrowing rules or provenance-preserving pointer displacement. Discarded increments use the same implementation.

&&, ||, and ?: now join modified source bindings alongside their expression results. Each arm starts with the state established by its condition, and skipped operands neither update bindings nor perform loads. The existing control analysis retains expression mutation facts in its single source traversal; translation consumes those facts and snapshots only changed bindings. Skipped logical operands publish their known boolean result directly.

The standalone corpus adds exact byte/64-bit wrap, signed decrement, nested lazy expressions, condition mutations, loop updates, and guarded pointer streams. It checks 532 scalar VM cases and 17 GPU inputs both normally and with device access sanitization, including complete outputs, unchanged inputs, and guard values. The existing attention, RMSNorm, and SwiGLU examples retain byte-identical HSACO.

The admitted destinations remain owned automatic integer and pointer bindings. Memory-element, vector, floating-point, const, and volatile updates retain source diagnostics; this change does not introduce an implicit storage model for them.