ci: retire legacy cron workflows + test_* rename + showcase_deploy webhook wiring

Retire 4 cron-based GH Actions workflows now replaced by showcase-ops
probe drivers:
- showcase_drift-detection.yml
- showcase_drift-report.yml
- showcase_redirect-report.yml
- showcase_smoke-monitor.yml

Standardise workflow naming (test_* prefix):
- e2e_dojo.yml → test_e2e-dojo.yml
- e2e_examples.yml → test_e2e-legacy-v1.yml
- showcase_aimock-e2e.yml → test_e2e-showcase-on-demand.yml
- test_doc-examples.yml → test_integration-docs.yml
- test_runtime-servers.yml → test_integration-runtime.yml
- starter_deployed_smoke.yml → test_smoke-starter-deployed.yml
- starter-smoke.yml → test_smoke-starter.yml

showcase_deploy.yml: POST deploy-result webhook to showcase-ops after
every deploy so the alert engine ingests the outcome (replaces the
inline Slack curl + GitHub status update).

static_check-binaries.yml: minor refresh for the new workflow names.

Author: jpr5