Release v0.4.0

Release v0.4.0

• Scaffolded Python templates now use ADK 2.0 GA. New adk, adk_a2a, and agentic_rag projects pin google-adk[gcp]>=2.0.0,<3.0.0; the [gcp] extra restores the OpenTelemetry GCP exporters and bundles the BigQuery client, so the separate [bigquery-analytics] extra is no longer needed. Cloud SQL sessions on Cloud Run and GKE keep working under 2.0. The bundled ADK coding skill and its reference docs were refreshed for 2.0.
  • #24
• Agent Runtime deploys no longer overwrite a user-supplied AGENT_VERSION (or NUM_WORKERS) passed via --update-env-vars, matching Cloud Run behavior. The "version not found" warning now names the pyproject.toml field to set.
• Fixed a stale deployment/terraform/dev/ path in the Cloud Trace observability guide so it matches the current single-project terraform layout.