## Summary
- make resolved turn environment shell metadata optional instead of
hard-coding bash
- render environment context shells from explicit environment metadata
when present, falling back to the existing session shell
- update environment context tests for inherited PowerShell-style
fallback and explicit per-environment shell override
## Testing
- Not run (not requested; formatted with `just fmt`).
Co-authored-by: Codex <noreply@openai.com>
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