refactor(main): add registry docs and fix registry save bug

[cuisongliu]

🤖 Generated by Copilot at 6b95139

Summary

🚚🐛📝

This pull request enhances the registry save command and its documentation, as well as the related buildimage and password packages. It fixes some bugs, simplifies some logic, and improves the clarity and consistency of the code and the docs. It also renames the --data-dir flag to --registry-dir in registry save.

The registry save command got a makeover
With better docs, flags, and error cover
The buildimage package
Got some logging and format baggage
And the password package removed some leftover

Walkthrough

• Simplify and update the registry save command and its documentation (link, link, link, link, link, link, link, link, link)
• Add error and debug log messages to the buildimage and registry packages (link, link, link)
• Remove unused and unnecessary code from the buildimage and password packages (link, link, link)

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (bf4ed66) 72.97% compared to head (8ce4139) 72.97%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3124   +/-   ##
=======================================
  Coverage   72.97%   72.97%           
=======================================
  Files           8        8           
  Lines         618      618           
=======================================
  Hits          451      451           
  Misses        132      132           
  Partials       35       35           

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