The workspace-scoped lock — the case where the surface was launched from the project
directory (Claude Code).
The newest lock that answers — VS Code's contributes.mcpServers launch does not
guarantee cwd is the workspace root, so the scoped path can miss a relay that is right
there.
Stale locks are unlinked as a side effect, which is what keeps the probe cost bounded.
Finds the live relay, or
nullwhen no client UI is running.