optimize tracing hot paths and add OOM protection

[theanuragg]

Improves the three hottest tracing code paths identified during profiling and adds OOM protection to TraceManager to prevent unbounded memory growth.

Changes

• OOM safeguard — introduce a maxTraces config option (default 0 = unlimited). When the limit is exceeded, evict the oldest traces from both traces[] and activeTraces, preventing unbounded growth in long‑running eval pipelines.
• createTraceApi — replace the recursive processSpans() closure with an explicit stack-based traversal to eliminate per‑level function call overhead when walking the span tree.
• convertSpanToApiSpan — remove dead _inputData / _outputData variables and seven redundant property reassignments, and move metadata into the initial object literal for a tighter hot path.
• createNestedSpansDict — inline the per‑call closure and drop the unused null‑coalescing logic around children for a simpler, cheaper span‑to‑dict conversion.

Performance

• createTraceApi (10 spans): 140,746 ops/s → 157,416 ops/s (+11.8%)
• createTraceApi (85 spans): 6,356 ops/s → 6,932 ops/s (+9.1%)
• observe() wrapper (no-op): 336,238 ops/s → 362,916 ops/s (+7.9%)

[vercel]

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