Explicit SSE close (sse.close)

Demonstrates ending a Server-Sent Events stream explicitly with $sse->close(reason => ...) rather than by returning from the handler.

pagi-server --app examples/sse-close/app.pl --port 5000
# then open http://localhost:5000/

The page opens an EventSource to /jobs. The server streams four progress events, then a done sentinel, then calls close(reason => 'job_complete').

What it shows:

• close(reason => ...) ends the stream immediately (decoupled from returning) and runs on_close. The reason is server-side only — printed to STDERR (SSE stream closed: reason=job_complete) and never sent to the client, because SSE has no close frame on the wire.
• Client-facing "why" is a normal event. The browser can't observe the close reason, so the app sends a done sentinel event; the client listens for it and calls es.close() to suppress the automatic reconnect.
• on_close runs however the stream ends — our close() here, or a client disconnect — so cleanup lives in one place.

See PAGI::Tools::Cookbook ("Closing an SSE stream, and recording why") and PAGI::Spec::Www ("Close SSE - send event").