[Feature] Graceful-shutdown wiring: HTTP unbind + cluster leave via CoordinatedShutdown + runUntilTerminated()

[pathosDev]

Use case

Every HTTP/cluster example hand-rolls the same shutdown choreography: process.on('SIGINT', ...) -> server.unbind() -> cluster.leave() -> system.terminate() — even though CoordinatedShutdown exists with phase-ordered shutdown. Users copy this boilerplate into production apps, usually getting the ordering or double-signal handling subtly wrong.

Proposed API

const server = await system.http(port).bind(routes);   // registers unbind in the service-unbind phase automatically
await system.runUntilTerminated();                     // installs SIGINT/SIGTERM handlers -> CoordinatedShutdown.run()

• HTTP bind and broker actors register their teardown in the appropriate CoordinatedShutdown phase on creation (opt-out via options).
• runUntilTerminated() (name open) resolves when the system has fully terminated; signal handlers are removed afterwards.
• Cross-runtime: signal handling goes through src/runtime/ (Bun/Node/Deno differences).

Acceptance criteria

• One-line graceful shutdown in every example; hand-rolled SIGINT choreography deleted
• Unbind/leave/terminate ordering guaranteed by CoordinatedShutdown phases
• Works on Bun, Node, Deno (smoke case)

Related

• [Feature] CoordinatedShutdown user-task injection at arbitrary phase #162 (CoordinatedShutdown user-task injection at arbitrary phase)