Extract _safe_write() helper that wraps end_headers() + wfile.write()
in try/except (BrokenPipeError, ConnectionResetError, ConnectionAbortedError,
TimeoutError, ssl.SSLError). Both j() and t() now use _safe_write()
instead of raw wfile calls.
Fixes cascading BrokenPipeError + SSL BAD_LENGTH crash when a client
disconnects mid-response and the error handler tries to write a 500
status through the same broken socket.
someaka