fix: stabilize file decorations and eliminate explorer flicker

[ozgen]

Use snapshot-based decoration updates instead of loading state during provideFileDecoration calls.

This removes redundant refreshes, prevents transient color changes in the Explorer, and keeps staged counts accurate.

[codecov-commenter]

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.69%. Comparing base (f35b7ac) to head (5252905).
⚠️ Report is 1 commits behind head on main.
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Additional details and impacted files

@@            Coverage Diff             @@
##             main      #35      +/-   ##
==========================================
+ Coverage   92.63%   92.69%   +0.06%     
==========================================
  Files          44       44              
  Lines        1399     1397       -2     
  Branches      320      320              
==========================================
- Hits         1296     1295       -1     
  Misses         28       28              
+ Partials       75       74       -1     

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