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

src/Core/ZB.MOM.WW.OtOpcUa.Core/Resilience/DriverResilienceOptions.cs

@@ -19,15 +19,17 @@ public sealed record DriverResilienceOptions
     public IReadOnlyDictionary<DriverCapability, CapabilityPolicy> CapabilityPolicies { get; init; }
         = new Dictionary<DriverCapability, CapabilityPolicy>();
 
-    /// <summary>
-    ///     Periodic scheduled recycle interval for Tier C out-of-process hosts, in seconds.
-    ///     Null (the default) = no scheduled recycle; the driver's Host process keeps running
-    ///     indefinitely unless a memory breach or operator action triggers a recycle. Only
-    ///     respected for <see cref="DriverTier.C"/>; Tier A/B recycle would tear down every
-    ///     OPC UA session, so the loader ignores non-null values for those tiers + logs a
-    ///     warning.
-    /// </summary>
-    public int? RecycleIntervalSeconds { get; init; }
+    // RecycleIntervalSeconds is GONE (Gitea #522). It configured a scheduled recycle of a Tier C
+    // driver's out-of-process Host — a process that no longer exists anywhere: Galaxy reaches MXAccess
+    // over gRPC to the external mxaccessgw sidecar (PR 7.2 retired the in-process Host/Proxy/Shared
+    // projects) and FOCAS has run in-process since its managed wire client landed 2026-04-24. The
+    // scheduler it fed was constructed only in tests, and IDriverSupervisor — the thing that would
+    // have performed the recycle — had zero implementations. The parser nevertheless validated the
+    // knob, so an operator could author a recycle interval through the AdminUI and get nothing.
+    //
+    // The JSON key is not an error if present: DriverResilienceOptionsParser ignores unknown keys, so
+    // a ResilienceConfig blob still carrying "recycleIntervalSeconds" parses cleanly and the value is
+    // simply dropped, which is what it already did in effect.
 
     /// <summary>
     ///     Look up the effective policy for a capability, falling back to tier defaults when no