Improve documentation and error messages for build options support

[Hellblazer]

Summary

Address code review feedback from PR #5 with documentation improvements and enhanced error messages.

Changes

1. Fix misleading recompile() javadoc (ComputeKernel.java:86-91)

   • Clarify that old kernel resources are released immediately during recompilation
   • Was incorrectly stating old kernel reference remains valid until explicitly closed
   • Now accurately documents the implementation behavior

2. Add thread safety documentation (ComputeKernel.java:93-96)

   • Document that isCompiled() may briefly return false during recompilation
   • Warn that concurrent execution from other threads will fail with IllegalStateException
   • Specify requirement for exclusive access during recompilation

3. Enhance error message (OpenCLKernel.java:92-93)

   • Suggest using recompile() when attempting double compilation
   • Guides users to the correct API for runtime kernel optimization

4. Add security documentation (ComputeKernel.java:57-59)

   • Document that build options are passed directly to compiler without sanitization
   • Warn callers to ensure options come from trusted sources only
   • Clarify backend compiler validation behavior

5. Simplify logging (OpenCLKernel.java:154-155)

   • Consolidated conditional logging into single statement
   • Uses ternary operator for cleaner code, same output

6. Add test documentation (ComputeKernelBuildOptionsTest.java)

   • Added javadoc to key test methods explaining their purpose:
     • testCompileWithDefine - preprocessor defines validation
     • testCompileWithCompilerFlags - performance optimization flags
     • testRecompileChangesDefineValue - auto-tuning workflow

Code Quality

• ✅ All improvements are documentation/messaging only - no functional changes
• ✅ No test failures
• ✅ Addresses all high and medium priority feedback items from code review

Feedback Addressed

From code-review-expert (9/10 score):

• High: Fix misleading recompile() documentation
• Medium: Add thread safety note to recompile() javadoc
• Low: Enhance error message in double-compilation check
• Low: Add security note about build options validation
• Low: Add javadoc to key test methods
• Low: Simplify logging format

References: Luciferase-qt0p (Phase 4 P4.1)