Fix Google Cloud VM Disk

My Compute Engine VM on Google Cloud will no longer let me in through SSH. All user accounts appear to have vanished and the boot disk throws errors. I can still reach the Google Cloud Console and I have already restarted the instance and built a fresh snapshot from the disk, but the snapshot refuses to mount or boot cleanly.

Your task is to diagnose and repair whatever is corrupt on the persistent disk so the VM becomes accessible again and my data is intact. I expect a clear explanation of what went wrong, the exact commands or console steps you used, and the final status of the disk.

Deliverables:
• Restore SSH (or Remote Desktop) access to the existing VM or to a new working instance built from the repaired disk.
• Recover the original user accounts and home directories, or provide a safe export of all data if full account recovery is impossible.
• Document each step performed in Google Cloud Console, including any use of snapshots, disk attaches, fsck, metadata changes, or startup-script fixes, so I can repeat the process if needed.

Please be comfortable working live in Compute Engine, manipulating snapshots and persistent disks, and running Linux file-system repairs. Once you feel confident you can resolve the disk error, let’s get started.