Overlapping InitializeAsync calls (the actor's fire-and-forget init plus a
retry tick) could leak an opened PLC connection and orphan a probe loop: no
gate guarded the lifecycle, only _gate for I/O.
- _lifecycleGate (the Modbus pattern) serialises Initialize / Reinitialize /
Shutdown / Dispose; teardown waits a bounded time, then tears down anyway.
- Every initialize and teardown starts a lifecycle generation. Health writes
(init, read/write passes, poll errors, shutdown) and the init publish carry
it and are dropped once it has moved on, so an abandoned init never
publishes over a later shutdown and a shutdown's final write never clobbers
a newer init. A superseded init disposes what it opened and throws.
- The init publish (options, tag tables, Plc, probe loop) happens under _gate;
the tag tables are built fresh and swapped by one reference write instead of
being cleared in place under live poll passes.
- Read/write passes re-check initialization under _gate, so a pass that waited
out a teardown cannot reopen a connection on a shut-down driver.
- The semaphores are no longer disposed: Dispose can race a running shutdown.
Refs #742
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
Joseph Doherty
ecf1e86464