fix(auth): re-establish auth guard in fork child; suppress EPIPE on peer-gone write

The deferred-message fork path (processDeferredMessages -> forkWithSocketPair)
never re-runs authenticateConnection, so the child inherited $connection->user
(passing the need_auth gate) but a cleared Auth guard — auth()->user() /
User::auth() returned null, crashing handlers that read the guard (learn-atc
GlitchTip #529/#532/#535/#531/#530). Sync the guard from the mock's user per
fork with Auth::setUser() (setUser, not login, to avoid re-firing the Login
event on every message).

Also guard SocketPairIpc::sendToParent with @socket_write: when the WS client
disconnects mid-response the parent tears down its read end, so the child's next
write races a closed pipe (EPIPE / "Broken pipe"). That benign warning was
promoted to a reported ErrorException and flooded GlitchTip (#461). Mirrors the
existing @fwrite in Broadcast/BroadcastClient.php.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/Ipc/SocketPairIpc.php

@@ -151,7 +151,13 @@ class SocketPairIpc
 
         // Newline-delimited framing
         $message = $data . "\n";
-        $written = socket_write($this->sockets[1], $message, strlen($message));
+        // Suppress the write warning: when the WS client disconnects mid-response
+        // the parent tears down its read end, so the child's next write races a
+        // closed pipe (EPIPE / "Broken pipe"). That warning is otherwise promoted
+        // to a reported ErrorException and floods GlitchTip for a benign, expected
+        // disconnect. The false-return is still handled by the caller. Mirrors the
+        // existing @fwrite in Broadcast/BroadcastClient.php.
+        $written = @socket_write($this->sockets[1], $message, strlen($message));
 
         return $written === strlen($message);
     }

src/Websocket/Handler.php

@@ -619,6 +619,29 @@ class Handler implements MessageComponentInterface
                 // Create mock that sends via socket pair
                 $mock = new MockConnectionSocketPair($connection, $ipc);
 
+                // Re-establish this fork's Laravel auth guard from the
+                // connection's user. authenticateConnection() logs the guard in,
+                // but it runs in the PARENT before forking — deferred messages
+                // fork later via processDeferredMessages() WITHOUT re-authenticating,
+                // and the parent's guard may since have been cleared (scheduleLogout)
+                // or reassigned to another connection. The mock still proxies the
+                // correct $connection->user (so the need_auth gate passes), yet
+                // auth()->user() / User::auth() would be null in this child —
+                // crashing any handler that reads the guard instead of ->user.
+                // Sync the guard to the connection here so every handler, deferred
+                // or not, sees a consistent authenticated user. setUser() (not
+                // login()) avoids re-firing the Login event on every message.
+                try {
+                    if ($mock->user) {
+                        Auth::setUser($mock->user);
+                    } elseif (Auth::hasUser()) {
+                        Auth::logout();
+                    }
+                } catch (\Throwable $authSyncError) {
+                    // Best-effort: the need_auth gate in controll_message() is
+                    // still the hard authorization check.
+                }
+
                 $this->executeControllerWithDbResilience(
                     $mock,
                     $channel,