fix(opcuaclient): review r0 minors m1-m10

- m1: the form hint now says ProbeTimeoutSeconds can only shorten Test Connect's
  10 s budget (passing the configured value as the button's budget is shared code -
  follow-up).
- m2: a superseded init no longer overwrites _options (generation-checked under
  _probeLock) or the cert-validation handler (handed back and published with the
  session; detached when not installed; a previous one detached on replace).
- m3: an ack none of whose condition ids resolves throws BadNodeIdUnknown + Warning.
- m4: an ack with no reply (transport failure / non-caller timeout) degrades.
- m5: no session before the gate is the same ServiceResultException(BadNotConnected).
- m6: the caller-cancelled-write deviation is documented.
- m7: a reply during a published outage advances the stamp but does not write
  Healthy; the keep-alive recovery ends the outage.
- m8: test for a non-caller OperationCanceledException write -> Degraded.
- m9: the browse session owns and disposes the user certificate it loaded
  (OpcUaUserIdentityFactory.LoadCertificate; a key-less cert is disposed before the
  throw); AdminUI-host certificate path documented.
- m10: a subscribe overtaken by a shutdown / re-init removes its half-built
  subscription instead of registering it (data and alarm).
- Sync Dispose drains each gate for 500 ms (was 2 s).

Refs #743

Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Shared/Drivers/Forms/OpcUaClientDriverForm.razor

@@ -219,7 +219,7 @@
             <div class="col-md-3">
                 <label class="form-label">Admin UI probe timeout (seconds)</label>
                 <InputNumber @bind-Value="_form.OpcUa.ProbeTimeoutSeconds" @bind-Value:after="EmitAsync" class="form-control form-control-sm" />
-                <div class="form-text">Max 60. Used by Test Connect. Default 15.</div>
+                <div class="form-text">Caps Test Connect: it can only shorten the 10 s Test Connect budget, never extend it.</div>
             </div>
         </div>
     </div>