Add integration tests for Proof Chain and Reachability workflows

- Implement ProofChainTestFixture for PostgreSQL-backed integration tests.
- Create StellaOps.Integration.ProofChain project with necessary dependencies.
- Add ReachabilityIntegrationTests to validate call graph extraction and reachability analysis.
- Introduce ReachabilityTestFixture for managing corpus and fixture paths.
- Establish StellaOps.Integration.Reachability project with required references.
- Develop UnknownsWorkflowTests to cover the unknowns lifecycle: detection, ranking, escalation, and resolution.
- Create StellaOps.Integration.Unknowns project with dependencies for unknowns workflow.

bench/baselines/performance-baselines.json

@@ -0,0 +1,22 @@
+{
+  "schema_version": "stellaops.perf.baselines/v1",
+  "updated_at": "2025-01-15T00:00:00Z",
+  "environment": {
+    "runtime": ".NET 10",
+    "os": "ubuntu-22.04",
+    "cpu": "8 cores",
+    "memory_gb": 16
+  },
+  "baselines": {
+    "score_computation_ms": 100,
+    "score_computation_large_ms": 500,
+    "proof_bundle_generation_ms": 200,
+    "proof_signing_ms": 50,
+    "dotnet_callgraph_extraction_ms": 500,
+    "reachability_computation_ms": 100,
+    "reachability_large_graph_ms": 500,
+    "reachability_deep_path_ms": 200
+  },
+  "threshold_percent": 20,
+  "notes": "Initial baselines established on CI runner. Update after algorithm changes."
+}