⚡ Optimize vector clock merge

[bmendonca3]

💡 What: Optimized mergeClocks in src/vectorClock.ts to iterate keys directly without creating intermediate Set and Array objects.

🎯 Why: The previous implementation created multiple temporary arrays (Object.keys) and a Set for every merge operation, causing unnecessary memory allocation and CPU overhead.

📊 Measured Improvement:
Benchmark with 10000 iterations of merging two 1000-key vector clocks (50% overlap):

• Baseline: ~1.79 ms per op
• Optimized: ~1.31 ms per op
• Improvement: ~26% speedup

Verified with new unit tests and existing smoke tests.

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PR created automatically by Jules for task 2477623390562674120 started by @bmendonca3

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