🔒 Fix unhandled directory creation failure in PluginResourceLoader

[RoiSoleil]

🎯 What: The vulnerability fixed
Addressed an issue where ensureStateExists ignored the return value of mkdir(), which could silently fail to create necessary state directories for user templates.

⚠️ Risk: The potential impact if left unfixed
A directory creation failure would fail silently. The caller would wrongly assume the directory exists, which could lead to exceptions later or undefined behavior, putting operations depending on the user template state at risk.

🛡️ Solution: How the fix addresses the vulnerability
Updated the directory creation code to capture the return value. To improve robustness, mkdirs() is used instead. If the directory creation fails, it handles race conditions by checking !exists(), and logs a descriptive error if the failure persists, returning false to notify the caller of the failure.

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PR created automatically by Jules for task 10781214918023215248 started by @RoiSoleil

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[codecov]

Codecov Report

❌ Patch coverage is 95.83333% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 73.42%. Comparing base (056906c) to head (f14e152).
⚠️ Report is 14 commits behind head on master.

Files with missing lines	Patch %	Lines
...ck/src/org/moreunit/mock/PluginResourceLoader.java	75.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #247      +/-   ##
============================================
+ Coverage     73.28%   73.42%   +0.14%     
- Complexity     3234     3247      +13     
============================================
  Files           420      422       +2     
  Lines         14435    14489      +54     
  Branches       1266     1268       +2     
============================================
+ Hits          10578    10639      +61     
+ Misses         3325     3316       -9     
- Partials        532      534       +2     

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