Doctor plugin checks: implement health check classes and documentation

Implement remediation-aware health checks across all Doctor plugin modules
(Agent, Attestor, Auth, BinaryAnalysis, Compliance, Crypto, Environment,
EvidenceLocker, Notify, Observability, Operations, Policy, Postgres, Release,
Scanner, Storage, Vex) and their backing library counterparts (AI, Attestation,
Authority, Core, Cryptography, Database, Docker, Integration, Notify,
Observability, Security, ServiceGraph, Sources, Verification).

Each check now emits structured remediation metadata (severity, category,
runbook links, and fix suggestions) consumed by the Doctor dashboard
remediation panel.

Also adds:
- docs/doctor/articles/ knowledge base for check explanations
- Advisory AI search seed and allowlist updates for doctor content
- Sprint plan for doctor checks documentation

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/__Libraries/StellaOps.Doctor.Plugins.ServiceGraph/Checks/MessageQueueCheck.cs

@@ -83,7 +83,8 @@ public sealed class MessageQueueCheck : IDoctorCheck
                     .WithRemediation(r => r
                         .AddManualStep(1, "Check RabbitMQ status", "docker ps | grep rabbitmq")
                         .AddManualStep(2, "Check RabbitMQ logs", "docker logs rabbitmq")
-                        .AddManualStep(3, "Start RabbitMQ", "docker-compose up -d rabbitmq"))
+                        .AddManualStep(3, "Start RabbitMQ", "docker-compose up -d rabbitmq")
+                        .WithRunbookUrl(""))
                     .WithVerification("stella doctor --check check.servicegraph.mq")
                     .Build();
             }
@@ -132,7 +133,8 @@ public sealed class MessageQueueCheck : IDoctorCheck
                     "Network unreachable")
                 .WithRemediation(r => r
                     .AddManualStep(1, "Start RabbitMQ", "docker-compose up -d rabbitmq")
-                    .AddManualStep(2, "Verify DNS", $"nslookup {rabbitHost}"))
+                    .AddManualStep(2, "Verify DNS", $"nslookup {rabbitHost}")
+                    .WithRunbookUrl(""))
                 .WithVerification("stella doctor --check check.servicegraph.mq")
                 .Build();
         }