fix: add error handling and resolve blocking plt.show in TVB components

[SandeepChauhan00]

Description

I ran into a couple of issues while testing the components
locally and wanted to fix them up.

connectivity.py:

• There was a duplicate import of Connectivity — it was
  imported at the top of the file and then again inside
  execute(). Cleaned that up by removing the one inside
  the method.

• plt.show() was blocking the entire workflow when running
  in non-interactive environments like JupyterLab or on a
  remote server. Changed it to plt.show(block=False) with
  a try/except fallback so it doesn't freeze things up if
  the environment can't display plots.

• Added error handling around Connectivity.from_file() —
  if someone passes in a bad file path, they now get a
  readable error message instead of a raw Python traceback.

• Also added a plot title so the connectivity matrix
  visualization is a bit easier to identify.

simulator.py:

• The simulator would crash with a confusing internal TVB
  error if connectivity wasn't connected. Added a quick
  check at the top of execute() that gives a clear message
  telling the user to connect a ConnectivityFromFile component.

• Wrapped simulator.configure() and simulator.run() in
  try/except blocks so that configuration or runtime failures
  produce helpful messages instead of raw tracebacks.

• Added basic timing — logs how long the simulation took,
  which is handy when experimenting with different parameters.

• Renamed the loop variable from time to time_data to
  avoid shadowing the time module that's now imported at
  the top.

Nothing should break — all the original behavior is preserved,
just with better error messages and a non-blocking plot.

References

N/A

Pull Request Type

• Xircuits Core (Jupyterlab Related changes)
• Xircuits Canvas (Custom RD Related changes)
• Xircuits Component Library
• Xircuits Project Template
• Testing Automation
• Documentation
• Others (Please Specify)

Type of Change

• New feature (non-breaking change which adds functionality)
• Bug fix (non-breaking change which fixes an issue)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Tests

Tested locally by:

1. Running ConnectivityFromFile with a valid default path —
   loads correctly and shows the plot without blocking.

2. Running ConnectivityFromFile with a bad file path —
   confirms the new error message appears instead of a
   raw traceback.

3. Running Simulator without connectivity connected —
   confirms the validation catches it and shows a clear
   message.

Tested on:

• Windows

Notes

Just wanted to make the components a bit more forgiving
for new users. If the approach looks good I'm happy to
apply similar improvements to other components too.