Complete batch 012 (golden set diff) and 013 (advisory chat), fix build errors

Sprints completed:
- SPRINT_20260110_012_* (golden set diff layer - 10 sprints)
- SPRINT_20260110_013_* (advisory chat - 4 sprints)

Build fixes applied:
- Fix namespace conflicts with Microsoft.Extensions.Options.Options.Create
- Fix VexDecisionReachabilityIntegrationTests API drift (major rewrite)
- Fix VexSchemaValidationTests FluentAssertions method name
- Fix FixChainGateIntegrationTests ambiguous type references
- Fix AdvisoryAI test files required properties and namespace aliases
- Add stub types for CveMappingController (ICveSymbolMappingService)
- Fix VerdictBuilderService static context issue

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

bench/golden-corpus/golden-sets/SYNTHETIC-TEST-001.golden.yaml

@@ -0,0 +1,70 @@
+# Golden Set: SYNTHETIC-TEST-001
+# Synthetic test case for unit testing
+#
+# Sprint: SPRINT_20260110_012_010_TEST
+# Task: GTV-002 - Synthetic Test Cases
+#
+# This is a minimal synthetic golden set for testing the diff layer pipeline
+# without requiring real binary fixtures.
+
+id: "SYNTHETIC-TEST-001"
+version: "1.0.0"
+created: "2026-01-11T12:00:00Z"
+author: "test-automation"
+status: "approved"
+
+# Synthetic component
+component:
+  name: "test-library"
+  ecosystem: "synthetic"
+  affectedVersions:
+    - ">=1.0.0,<1.0.5"
+
+# Synthetic vulnerability
+vulnerability:
+  cveId: "SYNTHETIC-TEST-001"
+  severity: "HIGH"
+  cvssScore: 7.5
+  description: "Synthetic vulnerability for testing fix verification pipeline"
+
+# Simple targets for testing
+targets:
+  - function: "vulnerable_function"
+    symbolPattern: "vulnerable_function"
+    description: "Simple vulnerable function for testing"
+    criticalEdges:
+      - from: "entry"
+        to: "sink_call"
+        description: "Entry to dangerous sink"
+    sinks:
+      - "dangerous_sink"
+    expectedPatchBehavior: "add_bounds_check"
+
+# Minimal witness
+witness:
+  command: "./test-binary --trigger"
+  inputs:
+    - name: "trigger.bin"
+      description: "Binary input that triggers the vulnerability"
+      trigger: "overflow"
+
+# Simple verification
+verification:
+  fixIndicators:
+    - type: "bounds_check_added"
+      location: "vulnerable_function"
+      pattern: "if.*len.*<"
+  expectedConfidence:
+    fixed: 0.95
+    partial: 0.60
+    inconclusive: 0.30
+
+# Test metadata
+metadata:
+  reviewedBy: "test-automation"
+  reviewedAt: "2026-01-11T12:00:00Z"
+  approvedFor: "testing"
+  synthetic: true
+  tags:
+    - "test"
+    - "synthetic"