End-to-end smoke test for the `tessl launch skill --cloud` pipeline. Reads one Linear issue (read-only) via the Linear API to prove `LINEAR_TOKEN` is wired into the sandbox, appends a single run-marker line to a log file, then opens a GitHub pull request with that one-line change to prove `GITHUB_TOKEN` and the publish path work. Use whenever you need to verify a cloud launch can reach Linear and GitHub and open a PR end to end -- dogfooding the launch pipeline, checking that credentials forward into the sandbox, or as a minimal known-good skill to launch when debugging the launch flow itself. Self-contained: driven by launcher-supplied inputs plus `LINEAR_TOKEN` and `gh` credentials in the environment. Makes no Linear writes; its only change is the one appended log line in the PR it opens.