Enhance README to clarify GCP Bucket and staging workspace generation rules

Updated the README to provide clearer descriptions for the `gcp-bucket-crossplane-health` and `stg-workspace-smoke` code bundles. The `gcp-bucket-crossplane-health` now specifies its focus on Kubernetes platform and k8s-kubectl-cmd runtime, while the `stg-workspace-smoke` is noted for its integration of runwhen and tool-builder runtime. This improves documentation clarity for users regarding the purpose and structure of these bundles.

codebundles/stg-workspace-smoke/.runwhen/generation-rules/stg-workspace-smoke.yaml

@@ -0,0 +1,23 @@
+apiVersion: runwhen.com/v1
+kind: GenerationRules
+spec:
+  platform: runwhen
+  generationRules:
+  - resourceTypes:
+    - workspace
+    matchRules:
+    - type: pattern
+      pattern: .+
+      properties:
+      - name
+      mode: substring
+    slxs:
+    - baseName: stg-smoke
+      qualifiers:
+      - workspace
+      baseTemplateName: stg-workspace-smoke
+      levelOfDetail: detailed
+      outputItems:
+      - type: slx
+      - type: runbook
+        templateName: stg-workspace-smoke-taskset.yaml