docs: add Google Colab setup and troubleshooting section

[minsuking]

Summary

Add a Colab-specific setup and troubleshooting section to README to help users run MONAI tutorials reliably on Google Colab.

Changes

• Document explicit installation of PyTorch 2.6.0 (CUDA 12.4) and MONAI 1.5 on Colab
• Add troubleshooting notes (torchaudio mismatch, filelock conflict, num_workers warning)
• Include a quick smoke test command to verify the setup

Motivation

Many users start with Colab and often hit dependency conflicts. This section improves first-time success and reproducibility.

[minsuking]

Hi, this is my first contribution to MONAI. Thank you for reviewing 🙏

I added a Google Colab setup & troubleshooting section to the README.
This helps users resolve common dependency issues when running MONAI tutorials on Colab.

Verified installation with PyTorch 2.6.0 + CUDA 12.4 and MONAI 1.5

Tested using unet_training_array.py tutorial → training ran successfully and produced expected Dice score

Documented known issues: torchaudio mismatch, filelock conflict, and num_workers guidance

This section should improve first-time success and reproducibility for Colab users.

[ericspod]

Hi @minsuking thanks for the contribution! I think it's fine as it is with a minor addition to change code in notebooks. I think notebook running in Colab is still fine with the environment that's installed, I just checked the MONAI 101 tutorial and I got Pytorch 2.8 that worked fine, but these instructions are good for install MONAI with other dependencies. It may be worth noting that people will usually run notebooks in Colab directly rather than install and run things on the command line.

[minsuking]

@ericspod Thank you very much for your kind review and guidance.
I’ve applied the suggested change as you recommended.
This was my first contribution to MONAI, and I really appreciate the opportunity to learn through the review process.
I’d also like to continue contributing in the future, especially by helping with bug fixes and improving documentation where it may be helpful.
Please let me know if there are specific areas where I can support.

[ericspod]

Looks good to me!

[ericspod]

Thanks again @minsuking If you're looking to contribute further we're putting together efforts on implementing work from MICCAI if that's of interest. Other than that we're always open to updates and fixes here in the tutorials. We do plan to reorganise and streamline things here soon as well.