`Errno::ECONNRESET` is a `SystemCallError`, not an `IOError`, so it was
not caught by the existing `rescue IOError, Errno::EPIPE` clauses. When
a client disconnected with a TCP RST during SSE notification broadcast,
the unhandled exception aborted the entire broadcast loop, causing
notifications to be lost for all remaining sessions.
This caused the `tools-call-with-logging` conformance scenario to fail
in CI (#248), where stale sessions from prior scenarios triggered
`ECONNRESET` on the first notification write, aborting the broadcast
and losing log notifications.
Add `Errno::ECONNRESET` to all four rescue clauses in
`StreamableHTTPTransport`: `send_notification` (targeted and broadcast),
`send_response_to_stream`, and `send_keepalive_ping`.
9c1c2491b1