Stop teaching sendable() as a liveness check

README.md

@@ -274,7 +274,6 @@ $server->addHttpHandler(function ($request, $response) {
             event: 'tick',            // addEventListener('tick', …) on the client
             id:    (string) $i,       // echoed back as Last-Event-ID on reconnect
         );
-        if (!$response->sendable()) break;   // peer gone — stop early
     }
 
     $response->end();

stubs/HttpResponse.php

@@ -152,7 +152,11 @@ public function getProtocolVersion(): string {}
     // === Body methods ===
 
     /**
-     * Write data to response body buffer
+     * Append data to the buffered response body.
+     *
+     * Nothing reaches the client here: the whole body goes out on end(),
+     * with Content-Length computed from it. Use send() to stream instead —
+     * that is the call which commits headers and applies backpressure.
      *
      * @param string $data Data to write
      * @return static
@@ -220,6 +224,10 @@ public function writeMessage(string $message): static {}
      * send() is always safe to call regardless; sendable() just lets a
      * handler do other work instead of blocking on a slow peer.
      *
+     * False does not report a departed client: a peer that is gone surfaces
+     * as HttpException 499 out of send(). A loop that breaks on false stops a
+     * stream that is merely slow.
+     *
      * @return bool
      */
     public function sendable(): bool {}