perf(controller): extend informer cache transform to Pod and CustomRun

Extend the cache transform to reduce memory usage for additional resource types:

**Pod Transform (for TaskRun controller)**
- 66.4% size reduction for realistic TaskRun pods
- Strips: ManagedFields, OwnerReferences, Labels, Finalizers,
  last-applied-configuration, and most Spec fields
- Preserves: Name, Namespace, Annotations, Spec.Containers[].Name
  (for status sorting), all Status fields

**Enhanced TaskRun Transform**
- For completed TaskRuns, now also strips:
  Status.Steps, Status.Sidecars, Status.PodName,
  Status.RetriesStatus, Status.CompletionTime
- Preserves: Status.Results, Status.Artifacts, Status.Conditions

**CustomRun Transform (new)**
- Strips: ManagedFields, last-applied-configuration
- For completed CustomRuns: Status.RetriesStatus, Status.CompletionTime
- Preserves: Status.Results, Status.Conditions

Adds kube_factory.go to wire the Pod transform into the Kubernetes
filtered informer factory used by the TaskRun controller.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: vdemeester

pkg/informer/transform/kube_factory.go

@@ -0,0 +1,80 @@
+/*
+Copyright 2026 The Tekton Authors
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package transform
+
+import (
+	"context"
+
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/client-go/informers"
+	client "knative.dev/pkg/client/injection/kube/client"
+	filteredFactory "knative.dev/pkg/client/injection/kube/informers/factory/filtered"
+	"knative.dev/pkg/controller"
+	"knative.dev/pkg/injection"
+	"knative.dev/pkg/logging"
+)
+
+func init() {
+	// Register our factory AFTER the default one to override it.
+	// This works because Knative's injection framework allows multiple
+	// registrations with the same key, and later ones override earlier ones.
+	injection.Default.RegisterInformerFactory(withTransformFilteredFactory)
+}
+
+// withTransformFilteredFactory creates a new filtered informer factory with the
+// Pod cache transform applied. This factory replaces the default Knative filtered
+// factory by using the same context key.
+//
+// This approach ensures that all Kubernetes Pod informers used by Tekton apply
+// the transform to reduce memory usage without modifying the generated code or
+// the Knative pkg.
+func withTransformFilteredFactory(ctx context.Context) context.Context {
+	c := client.Get(ctx)
+
+	// Get the label selectors from context (set by filteredinformerfactory.WithSelectors)
+	untyped := ctx.Value(filteredFactory.LabelKey{})
+	if untyped == nil {
+		// No selectors configured, let the default factory handle it
+		logging.FromContext(ctx).Debug("No label selectors configured for filtered factory, skipping transform")
+		return ctx
+	}
+
+	labelSelectors := untyped.([]string)
+	for _, selector := range labelSelectors {
+		selectorVal := selector
+		opts := []informers.SharedInformerOption{}
+
+		// Handle namespace scoping
+		if injection.HasNamespaceScope(ctx) {
+			opts = append(opts, informers.WithNamespace(injection.GetNamespaceScope(ctx)))
+		}
+
+		// Add label selector filter
+		opts = append(opts, informers.WithTweakListOptions(func(l *metav1.ListOptions) {
+			l.LabelSelector = selectorVal
+		}))
+
+		// Add our Pod cache transform
+		opts = append(opts, informers.WithTransform(TransformPodForCache))
+
+		// Store using the same Key as the default factory to override it
+		ctx = context.WithValue(ctx, filteredFactory.Key{Selector: selectorVal},
+			informers.NewSharedInformerFactoryWithOptions(c, controller.GetResyncPeriod(ctx), opts...))
+	}
+
+	return ctx
+}