Fix exhausted nodes not being retried when hard failure fills threshold

When all nodes are excluded/exhausted and a hard failure (not ResourceExhausted)
is the last error that fills the threshold, the exhausted nodes were never cleared
for retry. This fix checks and clears the exhausted pool before returning 'no nodes
available', allowing capacity-exhausted nodes to be retried as intended.

Author: cursoragent

packages/api/internal/orchestrator/placement/placement.go

@@ -62,7 +62,12 @@ func PlaceSandbox(ctx context.Context, algorithm Algorithm, clusterNodes []*node
 				skip[id] = struct{}{}
 			}
 			if len(skip) >= len(clusterNodes) {
-				return nil, errors.New("no nodes available")
+				if len(nodesExhausted) > 0 {
+					clear(nodesExhausted)
+					attempt++
+				} else {
+					return nil, errors.New("no nodes available")
+				}
 			}
 
 			node, err = algorithm.chooseNode(ctx, clusterNodes, skip, nodemanager.SandboxResources{CPUs: sbxRequest.GetSandbox().GetVcpu(), MiBMemory: sbxRequest.GetSandbox().GetRamMb()}, buildMachineInfo, labelFilteringEnabled, requiredLabels, affinityScores...)