fix(ws): hold SYNCING through post-connect status replay (#512)

[shbatm]

Summary

Fixes #512.

WebSocketClient.websocket() set ES_CONNECTED the instant the aiohttp socket opened, before the controller's post-connect status replay (a burst of ST/DON/DOF frames) drained. connection_events consumers that treat ES_CONNECTED as "the stream is now live" therefore saw the replay as live events, firing spurious triggers on every connect, config-entry reload, and WebSocket reconnect.

This is the direct backport of the already-shipped pyisyox fix (shbatm/pyisyox#170) and unblocks home-assistant/core#169782 (event platform for isy994).

Changes

• constants.py — add EventStreamStatus.SYNCING (+ ES_SYNCING alias). Pure-additive; no existing ES_* constant renamed or repurposed.
• events/websocket.py — on socket open, set ES_SYNCING (not ES_CONNECTED) and spawn a _promote_when_quiet() watcher:
  • Promotes to ES_CONNECTED once the replay goes quiet for WS_SYNC_QUIET_SECONDS (1.0s, no frame), with a hard cap WS_SYNC_MAX_SECONDS (10.0s) so a perpetually chatty controller can't stall the stream.
  • Sampled watcher (reads a per-frame counter) keeps the read loop a plain async for; cancelled in the read-loop finally, so a socket that drops before settling never reports CONNECTED.
  • Records still update during SYNCING (the dispatcher keeps feeding) — only the "stream is live" signal is withheld.
  • Re-armed on every reconnect. Status transitions now log at DEBUG.

Compatibility

• Public API surface unchanged; EventEmitter notifies the same way — consumers just receive one extra transition value during the ~1s sync window.
• HA Core isy994 only branches on CONNECTED / DISCONNECTED / LOST_STREAM_CONNECTION / RECONNECTING / RECONNECT_FAILED and gates entity availability on node.enabled (not isy.connected), so it is unaffected until it opts into gating event-style entities on connected. isy.connected simply turns true ~1s later.

Known limitation

The quiet window is anchored to socket-open, not to the first replayed frame (matching the validated pyisyox design). The IoX replay is cache-served on the subscribe round-trip, so the first frame is sub-second in practice; a pathologically delayed first frame (> the quiet window) is the accepted trade-off — anchoring on first-frame would regress a genuinely silent controller to the 10s cap.

Tests

tests/test_websocket_lifecycle.py (offline, no live ISY):

• _promote_when_quiet: silent-controller promote, holds-through-replay-then-promote, hard-cap under constant traffic.
• End-to-end through websocket(): replay routed (records update) while stream stays SYNCING, CONNECTED only after the quiet window.
• Socket drop before quiet → watcher cancelled, CONNECTED never emitted.

Full suite: 448 passed. pre-commit (ruff/codespell/prettier): clean.

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