e-stepper: Vertical off by default; the divider is remembered across runs

[martin-henz]

• The panes start side by side whatever the tab's width; only the user's Vertical choice stacks them (removes the width-based first choice).
• The arrangement and divider positions (stacked height, side-by-side share) are kept by the host plugin and passed to the view as `layout`, so a view mounted anew after a run starts from them.
• Tests: two stacked-layout tests click Vertical first; a new test covers remounting.

🤖 Generated with Claude Code

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Latest commit: d2a3362

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[martin-henz]

@codex review

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-11T03:54:18.197174Z	d2a3362	Manual request

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[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Swish!

Reviewed commit: d2a3362835

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