⚡ Bolt: [performance improvement] Replace replaceFirst with manual string logic

[RoiSoleil]

💡 What: Replaced regex String.replaceFirst with literal String.startsWith, endsWith, indexOf, and substring for simple modifications across four files (ExtensionField, InMemoryPath, ProjectPreferences, and RenameClassParticipant).
🎯 Why: Using replaceFirst forces Java to compile and match a regular expression on the fly, which introduces significant overhead for what should be simple string manipulation.
📊 Impact: Expected performance improvement ranges from a ~7x speedup (e.g., in ExtensionField and ProjectPreferences) up to a ~20x speedup (in InMemoryPath) for these operations. It also fixes subtle bugs where regexes incorrectly handled trailing commas or reserved characters.
🔬 Measurement: Verify by running the test suite (xvfb-run -a mvn -f org.moreunit.build/pom.xml test) and checking the provided benchmark comments inline in the modified files.

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PR created automatically by Jules for task 16202692058222164731 started by @RoiSoleil

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[codecov]

Codecov Report

❌ Patch coverage is 61.22449% with 19 lines in your changes missing coverage. Please review.
✅ Project coverage is 75.50%. Comparing base (c45130b) to head (af0b899).

Files with missing lines	Patch %	Lines
.../moreunit/core/preferences/ProjectPreferences.java	40.00%	6 Missing and 3 partials ⚠️
...ences/ProjectPreferencesStringReplacementTest.java	58.82%	6 Missing and 1 partial ⚠️
...g/moreunit/refactoring/RenameClassParticipant.java	66.66%	1 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #294      +/-   ##
============================================
- Coverage     75.67%   75.50%   -0.18%     
- Complexity     3378     3379       +1     
============================================
  Files           428      429       +1     
  Lines         14827    14871      +44     
  Branches       1288     1301      +13     
============================================
+ Hits          11221    11228       +7     
- Misses         3068     3101      +33     
- Partials        538      542       +4     

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