docs: name the workflows the prefixing sweep left behind

71888d86af moved twelve workflow files behind trigger prefixes and updated the
references GitHub validates. Three mentions in prose kept the old names: an echo
line, a file header and a lint's failure message. The same commit already fixed
the REST dispatch URL two lines below the echo it missed.

    roles/svc-runner/files/test/external.sh:36      test-runner-smoke.yml
    scripts/github/runner/cleanup_docker.sh:4       images-build-ci.yml
    tests/lint/repository/test_distros_spot.py:116  test-workspace.yml

None of them executes; the workflow-reference lint deliberately does not reach
them, because outside .github/workflows a bare *.yml collides with services.yml,
compose.yml and variants.yml. A repo-wide grep over all eleven legacy names now
returns nothing.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

scripts/github/runner/cleanup_docker.sh

@@ -1,7 +1,7 @@
 #!/usr/bin/env bash
 #
 # Cleanup pass for the Docker / buildx state on a GitHub-hosted runner.
-# Used by images-build-ci.yml as the always-on tail of the build job to
+# Used by call-images-build-ci.yml as the always-on tail of the build job to
 # free disk before the runner is reused (or recycled).
 set -euo pipefail