chore(audit): ScadaBridge C7 — perf re-baseline + CollapseAuditLogToCanonical projection test + index-test fix + dead-cref cleanup (Task 2.5)

Perf re-baseline (HotPathLatencyTests): empirical p95 on Apple M-series Release
build: 4KB DetailsJson slow path ≈14 µs, small-DetailsJson no-redactors ≈2 µs,
true no-op fast path ≈0 µs. Thresholds updated: 200 µs / 30 µs / 5 µs (≈15×
headroom for contested CI runners). Old thresholds (50 µs / 10 µs) were set for
the pre-C3 typed-field path; canonical JSON parse+rewrite is empirically faster.
Adds a third test (Filter_Apply_NoDetailsJson_FastPath) that asserts same-instance
return on the DetailsJson-null + within-cap fast path. Env-var overrides retained.

CollapseAuditLogToCanonicalMigrationTests (new): three MSSQL-gated [SkippableFact]
tests verifying Action/Category/Outcome projection, NULL Actor, DetailsJson codec
round-trip, and all six persisted computed columns (Kind/Status/SourceSiteId/
ExecutionId/ParentExecutionId) for ApiOutbound, InboundAuthFailure, and Failed-
status rows.

AddAuditLogTableMigrationTests: rename CreatesFiveNamedIndexes →
CreatesNineNamedIndexes; expand coverage from 5 original indexes to all 9 named
non-clustered indexes present after CollapseAuditLogToCanonical (adds
IX_AuditLog_Execution, IX_AuditLog_ParentExecution, IX_AuditLog_Node_Occurred,
UX_AuditLog_EventId).

Dead-cref cleanup: zero references to the deleted IAuditPayloadFilter /
DefaultAuditPayloadFilter / SafeDefaultAuditPayloadFilter types remain in any
.cs file (source or test). 26 occurrences across 13 files replaced with correct
references to IAuditRedactor / ScadaBridgeAuditRedactor / SafeDefaultAuditRedactor
or reworded as plain prose.

Residual sweep: no unused transitional code found beyond the acknowledged
"C3 transitional shim" comments on IngestedAtUtc stamping (active code, not dead).

src/ZB.MOM.WW.ScadaBridge.InboundAPI/Middleware/AuditWriteMiddleware.cs

@@ -59,9 +59,9 @@ namespace ZB.MOM.WW.ScadaBridge.InboundAPI.Middleware;
 /// <c>cap + 1</c> bytes per body even when the client streams hundreds of MiB.
 /// The downstream handler and the real client still see every byte; only the
 /// audit copy is bounded. The cap is also enforced again by
-/// <see cref="ZB.MOM.WW.ScadaBridge.AuditLog.Payload.DefaultAuditPayloadFilter"/> (which OR's
+/// <see cref="ZB.MOM.WW.ScadaBridge.AuditLog.Redaction.ScadaBridgeAuditRedactor"/> (which OR's
 /// in its own <see cref="AuditEvent.PayloadTruncated"/> determination), so a
-/// row truncated here remains truncated even if the filter is bypassed.
+/// row truncated here remains truncated even if the redactor is bypassed.
 /// </para>
 /// </summary>
 public sealed class AuditWriteMiddleware
@@ -118,9 +118,8 @@ public sealed class AuditWriteMiddleware
     {
         var sw = Stopwatch.StartNew();
 
-        // Per-request hot read of the inbound cap — mirrors the convention used
-        // by DefaultAuditPayloadFilter so a live config change picks up on the
-        // next request without re-resolving the singleton.
+        // Per-request hot read of the inbound cap so a live config change
+        // picks up on the next request without re-resolving the singleton.
         var cap = _options.CurrentValue.InboundMaxBytes;
 
         // Audit Log #23 (ParentExecutionId): mint the inbound request's per-request
@@ -428,7 +427,7 @@ public sealed class AuditWriteMiddleware
     /// and the boundary stands as-is.
     /// </summary>
     /// <remarks>
-    /// Mirrors the algorithm in <c>DefaultAuditPayloadFilter.TruncateUtf8</c>;
+    /// Mirrors the algorithm in <see cref="ZB.MOM.WW.ScadaBridge.AuditLog.Payload.AuditRedactionPrimitives.TruncateUtf8"/>;
     /// kept local to avoid a backwards project reference from
     /// ZB.MOM.WW.ScadaBridge.AuditLog into ZB.MOM.WW.ScadaBridge.InboundAPI.
     /// </remarks>