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.WebService/Program.cs

@@ -89,6 +89,18 @@ app.MapGet("/timeline/{eventId}", async (
     })
     .RequireAuthorization(StellaOpsResourceServerPolicies.TimelineRead);
 
+app.MapGet("/timeline/{eventId}/evidence", async (
+        HttpContext ctx,
+        ITimelineQueryService service,
+        string eventId,
+        CancellationToken cancellationToken) =>
+    {
+        var tenantId = GetTenantId(ctx);
+        var evidence = await service.GetEvidenceAsync(tenantId, eventId, cancellationToken).ConfigureAwait(false);
+        return evidence is null ? Results.NotFound() : Results.Ok(evidence);
+    })
+    .RequireAuthorization(StellaOpsResourceServerPolicies.TimelineRead);
+
 app.MapPost("/timeline/events", () => Results.Accepted("/timeline/events", new { status = "indexed" }))
     .RequireAuthorization(StellaOpsResourceServerPolicies.TimelineWrite);