fix(driver-focas): resolve Medium code-review finding (Driver.FOCAS-006)

EnsureConnectedAsync now disposes and nulls any existing non-connected
client before creating a fresh one via _clientFactory.Create().

Previously the method reused a cached client via ConnectAsync, but a
client disposed by a HandleRecycle race or prior teardown would hit
FocasWireClient.ThrowIfDisposed on every subsequent call, leaving the
device permanently wedged with BadCommunicationError and no recovery
path until ReinitializeAsync.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

code-reviews/Driver.FOCAS/findings.md

@@ -7,7 +7,7 @@
 | Review date | 2026-05-22 |
 | Commit reviewed | `76d35d1` |
 | Status | Reviewed |
-| Open findings | 7 |
+| Open findings | 6 |
 
 ## Checklist coverage
 
@@ -172,7 +172,7 @@ uses `ProbeLock`; apply the same discipline to driver health.
 | Severity | Medium |
 | Category | Error handling & resilience |
 | Location | `FocasDriver.cs:859-874`, `WireFocasClient.cs:22-31` |
-| Status | Open |
+| Status | Resolved |
 
 **Description:** `EnsureConnectedAsync` reuses the cached `IFocasClient` instance across
 a transient disconnect: it only checks `device.Client is { IsConnected: true }` and
@@ -191,7 +191,7 @@ as unrecoverable and recreate it from `_clientFactory`. Simplest: in
 null it before creating a fresh instance, rather than retrying `ConnectAsync` on the
 stale object.
 
-**Resolution:** _(open)_
+**Resolution:** Resolved 2026-05-22 — `EnsureConnectedAsync` now unconditionally disposes and nulls any existing non-connected client before calling `_clientFactory.Create()`, preventing `ObjectDisposedException` loops on a stale `WireFocasClient` after a `HandleRecycle` race or prior teardown.
 
 ### Driver.FOCAS-007