[ktz03]

Fixes #40, reported by @Artur-Minorius.

The first drag can draw points without updating widget.data, leaving data_as_pandas empty until a later click. The local drawing array aliases the widget model's array, so appending points changes the model value before model.set can detect a change. Drawing after a Python-side data replacement has the same problem.

Copy the array when initializing local drawing state and when receiving change:data. Pending points then stay local until the batch is published. Rebuild the checked-in JavaScript bundle with the repository's pinned esbuild 0.19.11.

Add real JupyterLab/browser regressions for initially empty data, constructor-provided data, and Python-side data replacement.

Validation on Windows, Python 3.12, JupyterLab 4.6.4, anywidget 0.11.0, ipywidgets 8.1.9 and headless Microsoft Edge:

• Full test suite: 4 passed. The same tests against unmodified production code give 3 failed, 1 passed; the three failures reproduce missing first-drag updates.
• Real-kernel checks also cover a subsequent click, reset, drawing after reset, undo, Python-side replacement, and pandas/polars/NumPy export row counts.
• Deterministic bundle rebuild, JavaScript syntax check, wheel build, installation and the CI import check pass.

Browser tests require pytest-playwright and jupyterlab as described in the test module; runtime dependencies are unchanged. Other notebook hosts, operating systems and Python versions were not tested.

[Artur-Minorius]

Thanks for fix!

Env: Windows, Python 3.13, anywidget 0.11.0 ipywidgets 8.1.9, VS Code Extension Jupyter 2025.9.1 and Jupyter Lab 4.3.5 on Waterfox