🔧 Revise execute tools to use `jupyter_mcp_tools` in JupyterLab mode

[eleonorecharles]

Description

When running in JupyterLab mode, revise the execution-related tooling so they delegate to the implementations provided by jupyter_mcp_tools.

The following tools are concerned:

• insert_execute_cell
• insert_cell
• execute_cell

Dependency

Wait for completion of this issue: datalayer/jupyter-mcp-tools#2

Implementation notes

• execute_cell should be realised using the existing select and run cell tools.
• Ensure these revisions only apply in JupyterLab mode and fall back to current behavior if Jupyerlab mode not enabled.