Use official JupyterLite lifecycle instead of fragile log-based readiness detection

[mohab-elshamy]

Background

The current Analysim–JupyterLite integration detects readiness by intercepting an internal log message:

"Pyodide contents will be synced with Jupyter Contents"

This approach is fragile since it depends on undocumented logging behavior and may break with future JupyterLite updates.

Solution

This PR introduces a pure frontend JupyterLab extension that:

• Uses the official plugin lifecycle
• Waits for app.restored to ensure JupyterLite is fully initialized
• Sends the readiness signal via:

window.parent.postMessage('jupyterlite-load', '*');

The extension is published on PyPI and added to requirements.txt, allowing anyone to install it easily:

analysim-jupyterlite-integration

Benefits

• Removes fragile console interception hacks
• Relies on stable, documented lifecycle APIs
• Improves maintainability and upgrade resilience
• Fully decouples Analysim from JupyterLite internals

Closes #114