test: add workflow visibility tests for poimen-harness namespace

Verify that WorkflowAdapter provides visibility into terminated workflows
in the poimen-harness namespace. This ensures namespace pass-down feature
is working correctly and users can specify different domains/namespaces
via X-Service: workflow requests.

Tests added:
1. integration-test.sh: Added workflow visibility tests
   - List workflows in poimen-harness namespace
   - Verify terminated/completed workflows are visible
   - Validate namespace parameter requirement
   - Check auth enforcement

2. workflow-visibility-test.sh: NEW dedicated workflow test script
   - Tests WorkflowAdapter namespace pass-down
   - Verifies list, describe, and auth enforcement
   - Specific focus on poimen-harness namespace
   - Looks for 4 terminated workflows

3. task-workflow-visibility.yaml: NEW Tekton task
   - Runs workflow visibility tests against live gateway
   - Sidecar deployment pattern
   - Publishes result + summary + workflow-count metrics

4. pipeline-sse-optimization.yaml: Updated
   - Added workflow-visibility-tests stage (runs after integration-tests)
   - Updated report-results to include workflow test results
   - Full pipeline now: integration → workflow-visibility → load → report

5. kustomization.yaml: Updated
   - Added task-workflow-visibility.yaml
   - Added workflow-visibility-test-script ConfigMap

This ensures that the deprecated /workflows endpoint replacement correctly
supports multi-tenant access via namespace specification in request payload.

k8s/tekton/kustomization.yaml

@@ -7,6 +7,7 @@ resources:
 - ci-rbac.yaml
 - task-integration-test.yaml
 - task-load-test.yaml
+- task-workflow-visibility.yaml
 - pipeline-sse-optimization.yaml
 
 generatorOptions:
@@ -19,3 +20,6 @@ configMapGenerator:
 - name: load-test-script
   files:
   - scripts/load-test.sh
+- name: workflow-visibility-test-script
+  files:
+  - scripts/workflow-visibility-test.sh