The Darwin-only debugger skip in `49fc92b0` passed the raw
`CI=true` env string to `skipif`, so `pytest` evaluated `true`
as Python source and failed at setup instead of skipping the
issue #320 node.
Cast `_ci_env` through `bool()` so the marker always receives
a boolean while retaining Linux coverage.
Prompt-IO: ai/prompt-io/opencode/20260820T135125Z_9f99043b_prompt_io.md
(this patch was generated in some part by `opencode` using
`gpt-5.6-sol` (`openai`))
Gud Boi