refactor(drivers): delete the inert driver-tier recycle machinery (#522)

The tier system was documented, operator-authorable, and inert. Deleted rather than activated,
because its premise is gone rather than merely unused.

"Tier C" meant a driver running out-of-process behind an IDriverSupervisor that could restart its
Host without tearing down the OPC UA session. No such process exists anywhere: Galaxy reaches
MXAccess over gRPC to the external mxaccessgw sidecar (PR 7.2 retired the in-process
Galaxy.Host/Proxy/Shared projects) and FOCAS has run in-process since its managed wire client
landed 2026-04-24. Consistently, IDriverSupervisor had ZERO implementations and there was nothing
for one to implement against.

The issue understated the inertness. It says the Tier-C-only protections never engaged, implying
the Tier A/B parts did. They did not: nothing constructs MemoryTracking, MemoryRecycle or
ScheduledRecycleScheduler outside their own unit tests, so the whole Core/Stability recycle layer
was dead — meaning option (a), "pass real tiers", was never a flag flip. It would have meant
writing the wiring that never existed AND arming it.

Deleted: MemoryTracking, MemoryRecycle, ScheduledRecycleScheduler, IDriverSupervisor, the
vestigial DriverTypeRegistry (referenced only by its own tests), and the RecycleIntervalSeconds
knob — which the AdminUI let an operator author and the parser validated while it configured
nothing.

DriverTier itself SURVIVES and is load-bearing: DriverResilienceOptions.GetTierDefaults supplies
the real per-capability timeout/retry/breaker policies via DriverFactoryRegistry.GetTier and
DriverCapabilityInvokerFactory. Only the isolation-and-recycle layer above it is gone.

Deliberately NOT deleted:

- WedgeDetector came along in the same directory and is equally dead in production, but it is
  tier-agnostic and is not recycle machinery — it only shares the folder. Restored rather than
  swept up in a decision that was not about it.
- IDriver.GetMemoryFootprint() and FlushOptionalCachesAsync() lose their only consumer here.
  Removing them touches all 12 drivers and every test stub, so they are documented as
  consumerless and filed as #525 instead of buried in this diff.

Compatibility: a deployed ResilienceConfig blob still carrying "recycleIntervalSeconds" parses
cleanly (unknown keys are ignored — guarded by a new test, because a blob that suddenly failed to
parse would fall back to tier defaults and silently discard the operator's real overrides), and
the AdminUI's preserve-unknown-keys bag keeps the key rather than rewriting stored config on an
unrelated edit.

The 01/U-6 knob-inertness guard carried an explicit carve-out admitting RecycleIntervalSeconds was
dormant and out of scope; that carve-out is now gone, so the expected set is literally what the
test's name claims.

Note: Host.IntegrationTests has 2 failures (DriverProbeRegistrationTests.is_idempotent,
PrimaryGateFailoverTests) — verified pre-existing by reproducing both on clean master dc9d947b.

Claude-Session: https://claude.ai/code/session_015p7wGqy3YpZNCpDzTpGMKo

tests/Core/ZB.MOM.WW.OtOpcUa.Core.Tests/Resilience/DriverResilienceOptionsTests.cs

@@ -15,14 +15,18 @@ public sealed class DriverResilienceOptionsTests
     ///     knob (the bulkhead genre this pass deleted) is inertness the interface-forwarding and
     ///     unwrapped-dispatch guards can't catch. To add a knob: wire it in <c>DriverResiliencePipelineBuilder</c>,
     ///     add a behavior test that proves it engages, THEN add it to the expected set below.
-    ///     (<c>RecycleIntervalSeconds</c> is itself Tier-C-dormant per 01/U-2 — a documented open question,
-    ///     explicitly out of this pass's scope; it stays in the expected list as the recycle scheduler, not
-    ///     the Polly pipeline, is its consumer.)
+    ///     <para><c>RecycleIntervalSeconds</c> used to sit in the expected set under an explicit carve-out —
+    ///     Tier-C-dormant per 01/U-2, "a documented open question, out of this pass's scope", justified by
+    ///     the recycle scheduler rather than the Polly pipeline being its consumer. Gitea #522 closed that
+    ///     question by deleting the scheduler (it was constructed only in tests, and the
+    ///     <c>IDriverSupervisor</c> that would perform the recycle had no implementations), so the knob went
+    ///     with it and the carve-out is gone. The expected set below is now literally what the name of this
+    ///     test claims.</para>
     /// </summary>
     [Fact]
     public void Options_properties_are_exactly_the_pipeline_wired_set()
     {
-        var expected = new[] { "Tier", "CapabilityPolicies", "RecycleIntervalSeconds" };
+        var expected = new[] { "Tier", "CapabilityPolicies" };
 
         var actual = typeof(DriverResilienceOptions)
             .GetProperties()