Shared GenServer dispatch logic for Run modules.

This module provides a __using__ macro that injects GenServer boilerplate, a common public API, and stdout dispatch logic for both the NIF-backed Denox.Run and the CLI-backed Denox.CLI.Run.

Public API (injected into using modules)

Lifecycle: start_link/1, stop/1

I/O: send/2, recv/2, send_and_recv/3

Pub/Sub: subscribe/1, unsubscribe/1

Introspection: alive?/1, os_pid/1

Convenience (one-shot):

• capture/1 — start, collect all lines, stop; returns {:ok, [String.t()]}
• stream/1 — start + lazy Stream (auto-stops on halt)
• stream_from/2 — lazy Stream from an existing PID (caller manages lifecycle)
• with_runtime/2 — start + user function + guaranteed stop via after

Implementing a Backend

Modules that use Denox.Run.Base, backend: :my_backend must implement four callbacks:

• init_backend/1 — start the backend (NIF resource or Port)
• send_backend/2 — write data to the backend's stdin
• stop_backend/1 — shut down the backend
• alive_backend?/1 — check if the backend is still running

See Denox.Run (NIF backend) and Denox.CLI.Run (subprocess backend) for concrete implementations.