## Why
Python SDK CI needs to exercise the checkout's CLI while retaining coverage of the wheel installation and its default runtime.
## What changed
- Run the Python SDK test suite against the same Bazel-built CLI as the TypeScript SDK tests. Build and stage `codex-code-mode-host` alongside the CLI so it can be discovered.
- Make the Python test harness prefer `CODEX_EXEC_PATH`, then a local debug build, then the installed runtime. Exclude optional turn-cost probes from recorded model requests.
- Add a separate installation job that builds the Python SDK wheel and installs it in a fresh environment.
## Testing
The installation smoke test verifies that imports resolve to the installed SDK and that its default runtime completes a mocked turn with the expected user input and final response.
GitOrigin-RevId: 8e3126742a014e2cf042afe799bc657e1ea2a282
