fix(EC-1816): use --images flag and document stress benchmark

Replace deprecated --json-input with --images, add benchmark listing
to README.

Resolves: EC-1816

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: dheerajodha

benchmark/README.md

@@ -10,3 +10,10 @@ other than any data that is contained within it. Benchmarks are run from within
 the directory they're defined in, simply by running `go run .`, additional
 arguments can be passed in, for example `-benchnum 10` to run the benchmark 10
 times.
+
+## Available benchmarks
+
+- **simple/** — Single-component validation against the `@redhat` policy collection.
+- **stress/** — Multi-component validation with configurable parallelism. Set
+  `EC_STRESS_COMPONENTS` (default 10) and `EC_STRESS_WORKERS` (default 35) to
+  control the workload.

benchmark/stress/stress.go

@@ -79,9 +79,9 @@ func setup() (string, suite.Closer) {
 }
 
 type component struct {
-	Name           string     `json:"name"`
-	ContainerImage string     `json:"containerImage"`
-	Source         *source    `json:"source,omitempty"`
+	Name           string  `json:"name"`
+	ContainerImage string  `json:"containerImage"`
+	Source         *source `json:"source,omitempty"`
 }
 
 type source struct {
@@ -156,7 +156,7 @@ func ec(dir string, components, workers int) func() {
 		if err := suite.Execute([]string{
 			"validate",
 			"image",
-			"--json-input",
+			"--images",
 			snap,
 			"--policy",
 			policy,