Implement Refined JUL Logging Strategy with ERROR/PERFORMANCE Prefixes

[Copilot]

This PR implements a comprehensive JUL (Java Util Logging) strategy following Oracle's official guidelines while adding practical compatibility enhancements for cloud monitoring and SLF4J/Log4j bridge users.

Key Changes

Lambda-Based Logging for Zero Runtime Overhead

All logging statements have been converted to use lambda expressions, ensuring the JVM automatically optimizes away unused log branches when log levels are disabled:

// Before: String concatenation always executes
LOGGER.fine("Debug info: " + expensiveOperation());

// After: Zero overhead when FINE level disabled
LOGGER.fine(() -> "Debug info: " + expensiveOperation());

ERROR Prefix for Cloud Monitoring Compatibility

Added "ERROR:" prefix to SEVERE level messages that warrant cloud monitoring attention, ensuring compatibility with teams using SLF4J/Log4j bridges that filter on ERROR strings rather than SEVERE:

// Security vulnerabilities now include ERROR prefix
LOGGER.severe(() -> "ERROR: StackOverflowError security vulnerability on file: " + filename);

Performance Warning Strategy

Implemented consistent "PERFORMANCE WARNING:" prefix for threshold violations logged at FINE level, following Oracle's guidance that performance issues should use FINE level:

LOGGER.fine(() -> "PERFORMANCE WARNING: Validation stack processing " + count + 
    " items exceeds recommended threshold of " + threshold);

Oracle JUL Level Hierarchy Compliance

Properly aligned all logging to Oracle's official target-audience-based hierarchy:

• SEVERE (1000): Critical failures preventing normal execution (+ ERROR prefix when appropriate)
• WARNING (900): Recoverable issues like encoding fallbacks
• INFO (800): Significant operational messages (class discovery, API comparison)
• CONFIG (700): Static configuration information (schema compilation details)
• FINE (500): Developer debugging and performance warnings
• FINER (400): Detailed method tracing and conditional validation branches
• FINEST (300): Maximum detail debugging for stack operations

Configuration Logging

Added CONFIG level logging for static configuration reporting, such as JSON schema compilation details that help with setup debugging.

Files Modified

• RobustCharDecoder.java: 6 logging statements converted to lambda expressions
• JsonTestSuiteSummary.java: StackOverflowError elevated to SEVERE with ERROR prefix
• JsonTestSuiteTest.java: Security vulnerability logging enhanced
• ApiTracker.java: 15 logging statements converted, error handling improved
• JsonSchema.java: Performance monitoring added, CONFIG logging for compilation
• AGENTS.md: Comprehensive logging strategy documentation added

Benefits

1. Oracle Compliance: Follows official JUL documentation and best practices
2. Cloud Compatibility: ERROR prefix ensures monitoring systems catch critical issues
3. Performance Awareness: Consistent threshold monitoring with clear prefixes
4. Zero Runtime Overhead: Lambda expressions eliminate performance impact when logging disabled
5. Developer Productivity: Clear level hierarchy for different debugging needs
6. Library Best Practices: Conservative logging approach appropriate for library consumers

Testing

All changes have been syntax-verified and follow established patterns in the codebase. The lambda-based logging approach ensures no performance regression while providing better debugging capabilities when needed.

Closes #34

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