dev(narugo): add nai metadata support (both read and write)

[narugo1992]

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[codecov]

Codecov Report

Attention: Patch coverage is 98.59813% with 3 lines in your changes missing coverage. Please review.

Project coverage is 99.12%. Comparing base (34af200) to head (713dbc4).
Report is 6 commits behind head on main.

Files with missing lines	Patch %	Lines
imgutils/sd/nai/extract.py	96.55%	2 Missing ⚠️
imgutils/sd/nai/inject.py	98.86%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #99      +/-   ##
==========================================
- Coverage   99.16%   99.12%   -0.05%     
==========================================
  Files          93       97       +4     
  Lines        2759     2973     +214     
==========================================
+ Hits         2736     2947     +211     
- Misses         23       26       +3     

Flag	Coverage Δ
unittests	99.12% <98.59%> (-0.05%)	⬇️

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