fix: batch stickiness — nodes in NodePriority finish all packages before new nodes are picked

Between packages, IntrospectNode transitions nodes from InProgress → Waiting,
causing getInProgressCount() to return 0 and createNewBatch() to pick new nodes
prematurely. With a Fixed 1-by-1 strategy, this meant all nodes processed in
parallel instead of sequentially.

GetNodesForNextBatch now checks NodePriority (via getStickyBatchNodes) before
falling through to createNewBatch. Nodes already in NodePriority that aren't
Complete are returned as the current sticky batch.

Author: lockwobr

.gitignore

@@ -6,4 +6,6 @@
 coverage.out
 
 # Symlinks created by Makefile build-cli
-k8s-tests/chainsaw/*/skyhook-cli
+k8s-tests/chainsaw/*/skyhook-cli
+docs/plans/*
+.claude/

operator/internal/wrapper/compartment.go

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: Copyright (c) 2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+ * SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
  * SPDX-License-Identifier: Apache-2.0
  *
  *
@@ -22,6 +22,10 @@ import (
 	"github.com/NVIDIA/skyhook/operator/api/v1alpha1"
 )
 
+// Compartment invariant: all nodes in a Compartment belong to the same Skyhook.
+// Compartments are populated per-Skyhook in BuildState and partitionNodesIntoCompartments,
+// so node.GetSkyhook() returns the same Skyhook for every node in the compartment.
+
 func NewCompartmentWrapper(c *v1alpha1.Compartment, batchState *v1alpha1.BatchProcessingState) *Compartment {
 	comp := &Compartment{
 		Compartment: *c,
@@ -112,10 +116,39 @@ func (c *Compartment) GetNodesForNextBatch() []SkyhookNode {
 		return c.getInProgressNodes()
 	}
 
+	// Sticky batch: nodes in NodePriority that aren't Complete yet should
+	// continue processing before we pick new nodes. This handles the case where
+	// IntrospectNode transitions nodes from InProgress → Waiting between packages.
+	if stickyNodes := c.getStickyBatchNodes(); len(stickyNodes) > 0 {
+		return stickyNodes
+	}
+
 	// No batch in progress, create a new one
 	return c.createNewBatch()
 }
 
+// getStickyBatchNodes returns nodes that are in NodePriority but not yet Complete.
+// These nodes were previously picked for a batch and should finish all their packages
+// before new nodes are selected.
+func (c *Compartment) getStickyBatchNodes() []SkyhookNode {
+	if len(c.Nodes) == 0 {
+		return nil
+	}
+
+	skyhook := c.Nodes[0].GetSkyhook()
+	if skyhook == nil || skyhook.Skyhook == nil || skyhook.Status.NodePriority == nil {
+		return nil
+	}
+
+	stickyNodes := make([]SkyhookNode, 0)
+	for _, node := range c.Nodes {
+		if _, inPriority := skyhook.Status.NodePriority[node.GetNode().Name]; inPriority && !node.IsComplete() {
+			stickyNodes = append(stickyNodes, node)
+		}
+	}
+	return stickyNodes
+}
+
 func (c *Compartment) getInProgressNodes() []SkyhookNode {
 	inProgressNodes := make([]SkyhookNode, 0)
 	for _, node := range c.Nodes {