test(e2e): add ExTester end-to-end test for the Deepnote notebook flow

[tkislan]

@coderabbitai ignore

Summary

Adds a black-box ExTester (vscode-extension-tester) E2E test that drives the full Deepnote happy path through the real VS Code UI: open a workspace folder + a one-notebook .deepnote file → create a Deepnote environment → select it for the notebook (kernel connects, venv + deepnote-toolkit provisioned) → Run All → assert the rendered output contains hello world.

What's included

• test/e2e/ — the suite (helloWorld.e2e.test.ts), config (tsconfig.json, .mocharc.js, settings.json), and the hello-world fixture
• package.json — vscode-extension-tester devDep + compile-e2e / setup:e2e* / test:e2e scripts
• .gitignore / .vscodeignore — ignore ExTester artifacts and keep them out of the packaged VSIX
• specs/e2e-extester-testing-plan.md — self-contained plan/reference, with a "§0 Implementation reality" section documenting the fixes below

Key fixes needed to pass headlessly

• Open the containing workspace folder (the serializer otherwise blocks on a "no workspace folder" snapshot warning) and open the notebook via Quick Open — ExTester's code -r reuse-window silently no-ops in the sandbox
• Accept the simple folder dialog via its OK button (Enter navigates into directories)
• Run via the toolbar "Run All" button, re-issued until output renders (deepnote.runallcells is gated behind context keys that are unset under automation)
• Idempotent environment creation with a stable name (reuses the venv)

No proposed-API grant needed

The extension declares Jupyter's enabledApiProposals, but the core flow (activation, the notebook serializer, kernel execution, output rendering) runs on stable VS Code APIs, so the suite runs on a plain stable VS Code with no product.json allow-listing — the way the published Marketplace / Open VSX extension runs for end users. (An earlier revision patched product.json; that was verified unnecessary and removed.)

How to run

npm run compile
npm run setup:e2e   # download test VS Code + ChromeDriver, install ms-python.python
xvfb-run --auto-servernum --server-args='-screen 0 1920x1080x24' npm run test:e2e

Verification

Verified passing locally on headless Linux (Xvfb, VS Code 1.111.0), with no proposed-API grant in product.json, including a clean-state run that provisions the venv from scratch:

✔ creates an environment, connects the kernel, runs the cell and renders output
1 passing

🤖 Generated with Claude Code

https://claude.ai/code/session_01LQk7n13UfmeDo2ujy8X4LX

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 0%. Comparing base (aef728e) to head (8bc972c).
✅ All tests successful. No failed tests found.

Additional details and impacted files

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