feat(specializer): M-cranelift stretch 1 opens — cranelift-jit 0.126 wired, in-tree JIT smoke green (TASK-44)

TASK-43 marked Done (PR #26 merged); TASK-44 stretch plan recorded in
backlog. cranelift-{jit,module,codegen,frontend} 0.126 added and a smoke
test JITs and executes a function on x86_64-pc-windows-msvc — the spike
result is now validated in-tree, not just in a note. The real per-row
backend (extern "C" fn(ctx) -> i64 ABI, coverage-first with shared
helpers, interpreter fallback) lands next per the stretch plan.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: ahrzb