mito-ai: add toolbar to .py file

[aarondr77]

Description

Here is the workflow of a user I talked to last week:

1. Create a notebook for some analysis
2. Turn it into an app
3. Make some change to the .py file manually
4. Close Mito
5. Reopen Mito and open the .py file
6. You want to preview it as an app again, but there is no app mode button. So instead, you ask the agent to turn it into an app. Since you don't have a notebook open, the agent says "I don't have notebook to turn into an app"
7. So instead, you copy and paste the .py file into a notebook and then ask it to create the app.

Now, if the .py file is a mito app (determined by the file name), then we inject an App Mode button into the .py file toolbar so you can open the preview. When you click the button, it searches for the notebook that has the associated name.

Testing

Steps:

1. Create an app
2. Close the notebook and preview
3. Open the .py file and click the app mode button. Make sure the app appears!

Documentation

Note if any new documentation needs to addressed or reviewed.

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Note

Medium Risk
Adds a new JupyterLab plugin that hooks into the file editor and opens notebooks via the contents API/doc manager, which could affect preview behavior and editor toolbar wiring. Dependency additions (@jupyterlab/fileeditor/@jupyterlab/docmanager) and metadata-based notebook lookup introduce some integration and edge-case risk.

Overview
Enables App Mode preview from the file editor by injecting an App Mode toolbar button when a user opens a mito-app-*.py file, and wiring the click to launch the existing Streamlit preview flow.

Adds helper logic to map an app file path to a notebook_id, locate an already-open notebook by metadata or scan/open a matching .ipynb in the same directory via the contents API, then call streamlitPreviewManager.openAppPreview.

Updates typings and dependencies to support IEditorTracker/IDocumentManager, exports MITO_NOTEBOOK_ID_KEY for metadata reads, and adjusts the UI test to run in Galata’s tmpPath.

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Project	Deployment	Actions	Updated (UTC)
monorepo	Ready	Preview, Comment	Mar 5, 2026 4:29am

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Cursor Bugbot has reviewed your changes and found 1 potential issue.

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Duplicated button creation logic across two handlers

Low Severity

The addAppModeButtonIfNeeded function and the widgetAdded callback contain ~30 lines of nearly identical logic: guard checks, ToolbarButton construction with the same configuration, and the same insertAfter/addItem fallback. This duplication means any future change (e.g., button label, class, or click behavior) needs to be updated in two places, risking inconsistency. A single helper like addButtonToWidget(widget) would eliminate this.

Additional Locations (1)

• mito-ai/src/Extensions/AppPreview/FileEditorAppModePlugin.tsx#L74-L103