slides: add cells with no output to the minimap & viewer

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📝 Summary

Because we allow code-edits for slides, there is a chance the slide may be edited to no longer produce an output, in which case it disappears. This adds a handling where we display all cells, and you can edit it to add to the deck.

Note that in a presentation, cells with no output are still skipped/hidden.

Screen.Recording.2026-06-03.at.2.25.46.PM.mov

I've also made the thumbnails in the minimap bigger and more readable.

📋 Pre-Review Checklist

• For large changes, or changes that affect the public API: this change was discussed or approved through an issue, on Discord, or the community discussions (Please provide a link if applicable).
• Any AI generated code has been reviewed line-by-line by the human PR author, who stands by it.
• Video or media evidence is provided for any visual changes (optional).

✅ Merge Checklist

• I have read the contributor guidelines.
• Documentation has been updated where applicable, including docstrings for API changes.
• Tests have been added for the changes made.

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Project	Deployment	Actions	Updated (UTC)
marimo-docs	Ready	Preview, Comment	Jun 3, 2026 6:28am

[cubic-dev-ai]

No issues found across 5 files

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[Copilot]

Pull request overview

This PR updates the slides authoring experience so cells that no longer render output (e.g., after code edits) still appear in the slides minimap and can be selected/edited, while remaining hidden/skipped during actual presentations.

Changes:

• Keep all cells in the slides “minimap order” list and track noOutputIds so output-less cells can be shown in the minimap/editor UI.
• Treat no-output cells as effectively skipped for reveal.js composition, and add a parked-preview overlay message/behavior when selected.
• Add a minimap thumbnail fallback for no-output cells that shows a small code preview.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
frontend/src/components/slides/reveal-component.tsx	Adds “parked preview” handling for selected no-output cells and ensures reveal composition skips them.
frontend/src/components/slides/minimap.tsx	Adds noOutputIds support and renders code thumbnails for no-output cells in the minimap.
frontend/src/components/editor/renderers/slides-layout/slides-layout.tsx	Wires slideCells/noOutputIds through the slides layout renderer to the minimap and deck viewer.
frontend/src/components/editor/renderers/slides-layout/compute-slide-cells.ts	Stops filtering out no-output cells; computes noOutputIds and treats them as effectively skipped.
frontend/src/components/editor/renderers/slides-layout/tests/compute-slide-cells.test.ts	Updates/extends tests to cover slideCells, noOutputIds, and starting-cell selection behavior.