feat(health): include degraded reasons in responses

ts/api/server.ts

@@ -210,6 +210,7 @@ export class ApiServer {
       const models = await this.containerManager.getAllAvailableModels();
 
       let status: 'ok' | 'degraded' | 'error' = 'ok';
+      const reasons = new Set<'unhealthy_container' | 'no_models_available' | 'gpu_detection_failed'>();
       const containerHealth: Record<string, 'healthy' | 'unhealthy'> = {};
       const gpuStatus: Record<string, 'available' | 'in_use' | 'error'> = {};
 
@@ -220,6 +221,7 @@ export class ApiServer {
         } else {
           containerHealth[id] = 'unhealthy';
           status = 'degraded';
+          reasons.add('unhealthy_container');
         }
       }
 
@@ -228,8 +230,14 @@ export class ApiServer {
         gpuStatus[gpu.id] = 'available';
       }
 
+      if (models.size === 0) {
+        status = 'degraded';
+        reasons.add('no_models_available');
+      }
+
       const response: IHealthResponse = {
         status,
+        reasons: Array.from(reasons),
         version: VERSION,
         uptime: Math.floor((Date.now() - this.startTime) / 1000),
         containers: statuses.size,
@@ -247,6 +255,7 @@ export class ApiServer {
       res.writeHead(500, { 'Content-Type': 'application/json' });
       res.end(JSON.stringify({
         status: 'error',
+        reasons: ['gpu_detection_failed'],
         error: error instanceof Error ? error.message : String(error),
       }));
     }