Resolves#17.
Part A: scripts/cleanup-rogue-workspaces.sh deletes workspaces whose id
or name starts with known test placeholder prefixes (aaaaaaaa-, etc.)
and force-removes the paired Docker container. Documented in
tests/README.md.
Part B: add a pre-flight check in provisionWorkspace() — when neither a
template path nor in-memory configFiles supplies config.yaml, probe the
existing named volume via a throwaway alpine container. If the volume
lacks config.yaml, mark the workspace status='failed' with a clear
last_sample_error instead of handing it to Docker's unless-stopped
restart policy (which otherwise loops forever on FileNotFoundError).
New pure helper provisioner.ValidateConfigSource + unit tests.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
