[merge: 214] refactor(runtime): split core runtime, expand module surface, and ship bytecode/JIT pipeline

• decompose monolithic runtime code (notably src/ant.c) into focused subsystems for errors, GC, runtime, REPL, ESM, bytecode execution, and module-specific paths
• add/extend built-in modules and headers (date, dns, module, napi, net, regex, tty, util, worker_threads, async_hooks, and related runtime wiring)
• land bytecode evaluation/entry-path improvements and integrate JIT execution scaffolding into the refactored runtime flow
• update public/internal headers and runtime APIs to match the new architecture
• remove legacy stack unit (include/stack.h, src/stack.c) and migrate behavior into the refactored runtime
• refresh build/package integration (meson deps/options, package metadata, zig pkg tooling, vendor wraps/packagefiles) for the new layout
• update examples/specs/type declarations and broaden regression/perf/GC/JIT coverage

BREAKING CHANGE: internal runtime structure and several internal interfaces were
reorganized; out-of-tree integrations depending on prior layout must be updated.