🎉 Initial commit

src/opcda_diagnozer/monitor/state.py

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+"""Connection state machine + reconnect backoff (SPECIFICATION §10.2).
+
+States: Connecting → Connected → ReconnectWait → Connecting …
+Backoff is exponential 1 s → 2 s → … capped at 60 s; every disconnect/reconnect
+pair is an event (D1/D2) with the outage duration computed and reported.
+
+The transition/backoff engine lands in Phase 1 (IMPLEMENTATION_PLAN §4.5).
+"""
+
+from __future__ import annotations
+
+from enum import Enum
+
+
+class ConnectionState(Enum):
+    """States of the connection state machine (SPECIFICATION §10.2)."""
+
+    CONNECTING = "connecting"
+    CONNECTED = "connected"
+    RECONNECT_WAIT = "reconnect_wait"