Handle terminal resize

[btwiuse]

Is your feature request related to a problem? Please describe.

Currently zasper web terminal doesn't resize to fit the window

Describe the solution you'd like

Make the terminal backend handle resize events emitted from the xterm.js frontend

Describe alternatives you've considered A clear and concise description of any alternative solutions or features you've considered.

• Manually resize using the resize command
• The terminal wire format currently in use comes from xterm-addon-attach, which is incompatible with https://github.com/jupyter/terminado used by Jupyter. Maybe zasper should move to the latter format

Additional context