feat: add PolicyPackSelectorComponent with tests and integration

- Implemented PolicyPackSelectorComponent for selecting policy packs.
- Added unit tests for component behavior, including API success and error handling.
- Introduced monaco-workers type declarations for editor workers.
- Created acceptance tests for guardrails with stubs for AT1–AT10.
- Established SCA Failure Catalogue Fixtures for regression testing.
- Developed plugin determinism harness with stubs for PL1–PL10.
- Added scripts for evidence upload and verification processes.

src/TimelineIndexer/StellaOps.TimelineIndexer/StellaOps.TimelineIndexer.Core/Abstractions/ITimelineQueryService.cs

@@ -6,4 +6,5 @@ public interface ITimelineQueryService
 {
     Task<IReadOnlyList<TimelineEventView>> QueryAsync(string tenantId, TimelineQueryOptions options, CancellationToken cancellationToken = default);
     Task<TimelineEventView?> GetAsync(string tenantId, string eventId, CancellationToken cancellationToken = default);
+    Task<TimelineEvidenceView?> GetEvidenceAsync(string tenantId, string eventId, CancellationToken cancellationToken = default);
 }

src/TimelineIndexer/StellaOps.TimelineIndexer/StellaOps.TimelineIndexer.Core/Abstractions/ITimelineQueryStore.cs

@@ -6,4 +6,5 @@ public interface ITimelineQueryStore
 {
     Task<IReadOnlyList<TimelineEventView>> QueryAsync(string tenantId, TimelineQueryOptions options, CancellationToken cancellationToken);
     Task<TimelineEventView?> GetAsync(string tenantId, string eventId, CancellationToken cancellationToken);
+    Task<TimelineEvidenceView?> GetEvidenceAsync(string tenantId, string eventId, CancellationToken cancellationToken);
 }

src/TimelineIndexer/StellaOps.TimelineIndexer/StellaOps.TimelineIndexer.Core/Models/TimelineEvidenceView.cs

@@ -0,0 +1,16 @@
+namespace StellaOps.TimelineIndexer.Core.Models;
+
+/// <summary>
+/// Evidence linkage for a timeline event, pointing to sealed bundle/attestation artifacts.
+/// </summary>
+public sealed class TimelineEvidenceView
+{
+    public required string EventId { get; init; }
+    public required string TenantId { get; init; }
+    public Guid? BundleId { get; init; }
+    public string? BundleDigest { get; init; }
+    public string? AttestationSubject { get; init; }
+    public string? AttestationDigest { get; init; }
+    public string? ManifestUri { get; init; }
+    public DateTimeOffset CreatedAt { get; init; }
+}

src/TimelineIndexer/StellaOps.TimelineIndexer/StellaOps.TimelineIndexer.Core/Services/TimelineQueryService.cs

@@ -19,6 +19,37 @@ public sealed class TimelineQueryService(ITimelineQueryStore store) : ITimelineQ
         return store.GetAsync(tenantId, eventId, cancellationToken);
     }
 
+    public async Task<TimelineEvidenceView?> GetEvidenceAsync(string tenantId, string eventId, CancellationToken cancellationToken = default)
+    {
+        ArgumentException.ThrowIfNullOrWhiteSpace(tenantId);
+        ArgumentException.ThrowIfNullOrWhiteSpace(eventId);
+        var evidence = await store.GetEvidenceAsync(tenantId, eventId, cancellationToken).ConfigureAwait(false);
+        if (evidence is null)
+        {
+            return null;
+        }
+
+        var manifest = evidence.ManifestUri;
+        if (manifest is null && evidence.BundleId is not null)
+        {
+            manifest = $"bundles/{evidence.BundleId:N}/manifest.dsse.json";
+        }
+
+        var subject = evidence.AttestationSubject ?? evidence.BundleDigest;
+
+        return new TimelineEvidenceView
+        {
+            EventId = evidence.EventId,
+            TenantId = evidence.TenantId,
+            BundleId = evidence.BundleId,
+            BundleDigest = evidence.BundleDigest,
+            AttestationSubject = subject,
+            AttestationDigest = evidence.AttestationDigest,
+            ManifestUri = manifest,
+            CreatedAt = evidence.CreatedAt
+        };
+    }
+
     private static TimelineQueryOptions Normalize(TimelineQueryOptions options)
     {
         var limit = options.Limit;