mild fix capture board image shortcut

[sensuikan1973]

resolve #2835

[gemini-code-assist]

Code Review

This pull request includes important fixes that enhance both the reliability of integration tests and the robustness of the application's image capture functionality. The keyboard event simulation in tests has been made more accurate, and a critical check for the existence of temporary directories has been added to prevent potential file system errors during image saving. These changes improve the overall stability and correctness of the application.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.98%. Comparing base (21e8117) to head (d177cc1).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2836   +/-   ##
=======================================
  Coverage   93.97%   93.98%           
=======================================
  Files          52       52           
  Lines        1477     1479    +2     
=======================================
+ Hits         1388     1390    +2     
  Misses         89       89           

Flag	Coverage Δ
integration_test	65.44% <100.00%> (+0.11%)	⬆️
macos-latest	93.03% <100.00%> (+2.64%)	⬆️
ubuntu	93.44% <100.00%> (+<0.01%)	⬆️
widget_test	90.26% <0.00%> (-0.13%)	⬇️
windows	93.44% <100.00%> (+<0.01%)	⬆️

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Files with missing lines	Coverage Δ
.../pedax_shortcuts/capture_board_image_shortcut.dart	100.00% <100.00%> (ø)

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