feat(threading): implement Job System with work-stealing thread pool …

[LyeZinho]

…(RF2.2-RF2.6)

Work-stealing thread pool with per-worker deques, 3 priority levels (Critical/Normal/Background), JobHandle index+version tracking, JobBarrier group synchronization, and scheduleParallelFor.

• JobPriority enum with Critical > Normal > Background ordering
• IJob virtual interface + JobWithData type-safe zero-alloc jobs
• JobHandle with atomic completion flag (index+version avoids ABA)
• JobBarrier with condition_variable for group wait
• JobSystem: N-1 worker threads, priority-ordered execution, work-stealing from other workers when idle
• scheduleData convenience template
• scheduleParallelFor chunked across workers
• waitAll with condition_variable notification
• Stats tracking (active workers, pending, completed, avg time)
• 41 tests, 1054 assertions (incl. 10K/100K stress tests)

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File	Description
src/threading/JobSystem.hpp	Caffeine::Threading — JobPriority, IJob, JobWithData, JobHandle (index+version), JobBarrier, JobSystem class with work-stealing
src/threading/JobSystem.cpp	Thread pool (N-1 workers), priority-ordered execution (Critical→Normal→Background), work-stealing from other workers, condition_variable sleep/wake, stats tracking
tests/test_jobsystem.cpp	41 tests, 1054 assertions — priority enum, IJob/JobWithData, JobHandle, JobBarrier, scheduling, scheduleData, parallelFor, waitAll, stats, stress tests (1K, 10K, 100K jobs), priority starvation test
CMakeLists.txt	Added src/threading/JobSystem.cpp to lib sources
tests/CMakeLists.txt	Added test_jobsystem.cpp

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