v1.16.11-test1

Fix four correctness and robustness issues

- connection.py: coerce scalar rows to 1-tuple in _iquery() numpy path
  so single-column structured ndarrays don't break zip(names, row).

- json.py: use integer arithmetic (days/seconds/microseconds) instead
  of float total_seconds() for timedelta serialization to avoid
  precision loss on large durations.

- registry.py: guard numpy import in _normalize_vector_output() behind
  try/except ImportError so non-numpy environments (WASM) can still
  use vector formats like 'list'.

- server.py: use pre-allocated bytearray in _read_pipe_message() to
  avoid quadratic copying, and enforce a 16 MiB size cap to prevent
  unbounded memory growth from malformed length prefixes.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>