fix: return the degraded deep-health report instead of throwing

The API answers GET /v1/health/deep with 503 and a full report when a
dependency is down. handleResponse treated that as an error, so
deepHealth() could never report a degraded status. The Go SDK already
accepts 503 for this endpoint.

Claude-Session: https://claude.ai/code/session_01Agoc9bRVE9KL7mmWtey9Vq

src/client.ts

@@ -285,9 +285,13 @@ export class ElydoraClient {
     return handleResponse<HealthResponse>(res);
   }
 
+  /** 503 carries the degraded report, not an error. */
   async deepHealth(): Promise<DeepHealthResponse> {
     const url = `${this.baseUrl}/v1/health/deep`;
     const res = await fetch(url, { method: 'GET', headers: { 'Accept': 'application/json' } });
+    if (res.status === 503) {
+      return (await res.json()) as DeepHealthResponse;
+    }
     return handleResponse<DeepHealthResponse>(res);
   }