Production-ready updates: symlink support and debug cleanup

[jjroelofs]

Summary

This issue consolidates production-ready improvements including enhanced symlink compatibility, security hardening, and debug cleanup across the RL module.

Changes Made

• Enhanced rl.php endpoint with symlink support: Added fallback path detection using $_SERVER['SCRIPT_FILENAME'] for symlinked module development setups
• Security improvements: Input validation for experiment UUIDs and arm IDs using regex patterns
• Thompson sampling tie-breaker: Added micro-randomization to prevent identical scores
• Debug cleanup: Removed all debug logging statements from production code
• Code optimization: Simplified conditional logic and removed verbose comments

Technical Details

rl.php Endpoint Enhancement

• Primary path detection: chdir('../../../') for standard installations
• Fallback detection: Uses $_SERVER['SCRIPT_FILENAME'] when symlinks are present
• Input sanitization: Regex validation for security (/^[a-zA-Z0-9]+$/ for UUIDs)
• Error handling: Proper HTTP status codes (400, 500) with descriptive messages

Thompson Sampling Improvements

• Added tie-breaker mechanism: $base_score + $tie_breaker where tie-breaker = mt_rand(1, 999) / 1000000
• Ensures unique scores even when beta distributions return identical values
• Maintains statistical properties while preventing deterministic ordering

Production Cleanup

• Removed debug statements from ExperimentDataStorage.php and ExperimentManager.php
• Simplified time window logic to ternary operators
• Removed verbose code comments, keeping only essential documentation
• Code passes Drupal coding standards

Testing

• Symlink compatibility verified with development setups
• Path detection fallback tested with both standard and symlinked installations
• Thompson sampling randomization confirmed working
• All Drupal coding standards checks pass

Compatibility

• Drupal 10/11 compatible
• Works with both standard and symlinked module installations
• Backward compatible with existing experiment data
• No database schema changes required

Pull Request: #8
Related to AI Sorting module cold start fix: dxpr/ai_sorting#10

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