feat(health): AuditRedactionFailure counter + bridge (#23 M5)

Bundle C task M5-T7 — surface DefaultAuditPayloadFilter redactor
over-redactions as a Site Health metric so a misconfigured /
catastrophic regex shows up on /monitoring/health rather than
disappearing into a NoOp sink.

  - SiteHealthReport: new 'AuditRedactionFailure' int field
    (defaulted to 0 for back-compat with existing producers/tests).
  - ISiteHealthCollector / SiteHealthCollector:
    new IncrementAuditRedactionFailure() — per-interval atomic
    counter with Interlocked, reset on CollectReport, mirroring
    the M2 Bundle G SiteAuditWriteFailures pattern.
  - HealthMetricsAuditRedactionFailureCounter: new bridge in
    ScadaLink.AuditLog.Site that forwards IAuditRedactionFailureCounter
    increments to ISiteHealthCollector — mirrors
    HealthMetricsAuditWriteFailureCounter one-for-one.
  - AddAuditLogHealthMetricsBridge: now ALSO Replaces the
    NoOpAuditRedactionFailureCounter binding with the health-metrics
    bridge, so a single AddAuditLogHealthMetricsBridge() call wires
    both the M2 Bundle G write-failure counter and the M5 Bundle C
    redaction-failure counter into the health report.

Site-side only for M5 — the filter also runs on CentralAuditWriter
and AuditLogIngestActor (where it just keeps the NoOp default), but
a central-side health-metric surface for AuditRedactionFailure is
deferred to M6 alongside the rest of the central health collector
work.

Tests:
  - AuditRedactionFailureMetricTests (HealthMonitoring) covers the
    SiteHealthCollector increment/report/reset shape (3 tests).
  - HealthMetricsAuditRedactionFailureCounterTests (AuditLog) covers
    the AuditLog → HealthMonitoring bridge (3 tests).
  - Existing CountCapturingHealthCollector stub in
    DeploymentManagerRedeployTests extended with the new no-op
    interface method.

Verified: dotnet build clean, all 24 test projects green
(the only Failed at first ScadaLink.SiteRuntime.Tests run was the
known-flaky InstanceActorChildAttributeRaceTests; passes on re-run
in isolation and full suite, unrelated to these changes).

src/ScadaLink.HealthMonitoring/ISiteHealthCollector.cs

@@ -19,6 +19,15 @@ public interface ISiteHealthCollector
     /// <c>AddAuditLogHealthMetricsBridge()</c>.
     /// </summary>
     void IncrementSiteAuditWriteFailures();
+    /// <summary>
+    /// Audit Log (#23) M5 Bundle C — increment the per-interval count of
+    /// payload-filter redactor over-redactions (header / body / SQL
+    /// parameter stage throws routed to the
+    /// <c>&lt;redacted: redactor error&gt;</c> marker). Bridged from the
+    /// <c>IAuditRedactionFailureCounter</c> binding registered via
+    /// <c>AddAuditLogHealthMetricsBridge()</c>.
+    /// </summary>
+    void IncrementAuditRedactionFailure();
     void UpdateConnectionHealth(string connectionName, ConnectionHealth health);
     void RemoveConnection(string connectionName);
     void UpdateTagResolution(string connectionName, int totalSubscribed, int successfullyResolved);

src/ScadaLink.HealthMonitoring/SiteHealthCollector.cs

@@ -14,6 +14,7 @@ public class SiteHealthCollector : ISiteHealthCollector
     private int _alarmErrorCount;
     private int _deadLetterCount;
     private int _siteAuditWriteFailures;
+    private int _auditRedactionFailures;
     private readonly ConcurrentDictionary<string, ConnectionHealth> _connectionStatuses = new();
     private readonly ConcurrentDictionary<string, TagResolutionStatus> _tagResolutionCounts = new();
     private readonly ConcurrentDictionary<string, string> _connectionEndpoints = new();
@@ -74,6 +75,20 @@ public class SiteHealthCollector : ISiteHealthCollector
         Interlocked.Increment(ref _siteAuditWriteFailures);
     }
 
+    /// <summary>
+    /// Audit Log (#23) M5 Bundle C — increment the per-interval count of
+    /// payload-filter redactor over-redactions (header / body / SQL
+    /// parameter stages routed to the
+    /// <c>&lt;redacted: redactor error&gt;</c> marker). Bridged from the
+    /// <c>IAuditRedactionFailureCounter</c> binding registered via
+    /// <c>AddAuditLogHealthMetricsBridge()</c>; reset every interval together
+    /// with the other per-interval counters.
+    /// </summary>
+    public void IncrementAuditRedactionFailure()
+    {
+        Interlocked.Increment(ref _auditRedactionFailures);
+    }
+
     /// <summary>
     /// Update the health status for a named data connection.
     /// Called by DCL when connection state changes.
@@ -158,6 +173,7 @@ public class SiteHealthCollector : ISiteHealthCollector
         var alarmErrors = Interlocked.Exchange(ref _alarmErrorCount, 0);
         var deadLetters = Interlocked.Exchange(ref _deadLetterCount, 0);
         var siteAuditWriteFailures = Interlocked.Exchange(ref _siteAuditWriteFailures, 0);
+        var auditRedactionFailures = Interlocked.Exchange(ref _auditRedactionFailures, 0);
 
         // Snapshot current connection and tag resolution state
         var connectionStatuses = new Dictionary<string, ConnectionHealth>(_connectionStatuses);
@@ -190,6 +206,7 @@ public class SiteHealthCollector : ISiteHealthCollector
             DataConnectionTagQuality: tagQuality,
             ParkedMessageCount: Interlocked.CompareExchange(ref _parkedMessageCount, 0, 0),
             ClusterNodes: _clusterNodes?.ToList(),
-            SiteAuditWriteFailures: siteAuditWriteFailures);
+            SiteAuditWriteFailures: siteAuditWriteFailures,
+            AuditRedactionFailure: auditRedactionFailures);
     }
 }