0.5.2 — DX hardening for hardware engineers

[0.5.2] - 2026-05-21 - DX hardening for hardware engineers

Fixed

• Error messages now reference plexus init instead of the non-existent plexus start.
• close() now attempts to flush any buffered points before tearing down the transport,
  preventing silent data loss on graceful shutdown.
• persistent_buffer default changed from False to True — store-and-forward is now
  on by default, matching the ~/.plexus/config.json default and the right choice for
  field hardware. Pass persistent_buffer=False to opt out (e.g. in test fixtures).

Added

• send_batch() now accepts 3-tuples (metric, value, timestamp) alongside the existing
  2-tuple form. Per-point timestamps let sensors on different interrupt timers share a
  single batch call. 2-tuples continue to use the shared timestamp argument.
• on_command() now warns immediately via stderr if called after the WebSocket has already
  authenticated, making the "register before first send()" ordering requirement visible
  rather than silently broken.
• source_id is validated against ^[a-z0-9][a-z0-9_-]{1,62}$ at construction time.
  Invalid names now raise ValueError with a clear message instead of failing obscurely
  at the gateway.

Changed

• _say() / _QUIET consolidated into a new internal plexus/_log.py module.
  Previously duplicated verbatim between client.py and ws.py.