Rework performance benchmarks around serializer-only slices

[Copilot]

The performance suite was dominated by NATS transport and too many iterations, which made runs slow and obscured serializer behavior. This reworks the harness to measure only Serializer.serialize/Serializer.deserialize size and timing, while making targeted slices cheap to run.

• Scope the benchmark to codec work

  • Removed local/remote NATS setup and all transport latency measurements from the harness.
  • Replaced request/response round-trip benchmarking with direct request/response serialization and deserialization measurement in Python, TypeScript, and Java.
  • Kept Telepact JSON, Telepact binary, Telepact packed binary, protobuf, and plain JSON comparisons.

• Reduce run cost and support slices

  • Lowered steady-state sampling to 20 iterations.
  • Limited warmup to a single binary cache warmup for Telepact binary modes.
  • Added filters for --languages, --data-shapes, --collection-shapes, and --methods so slices can be run without executing the full matrix.

• Align shared outputs with the new model

  • Simplified shared metrics to codec-only timings:
    • requestSerializationTimeNs
    • requestDeserializationTimeNs
    • responseSerializationTimeNs
    • responseDeserializationTimeNs
  • Removed network metadata from generated summaries and CSV/JSON outputs.
  • Regenerated the committed benchmark summary artifacts from the updated harness.

• Trim perf-only dependencies

  • Removed NATS dependencies from the performance test projects.
  • Added a small Java serializer factory helper so the benchmark can construct client/server serializers directly without transport plumbing.

• Refresh docs and examples

  • Updated the binary performance guide to describe the serializer-only benchmark and the new results.
  • Documented slice-oriented usage for quick reruns.

cd test/performance

uv run python -m perf_harness.run \
  --languages python \
  --data-shapes all-numbers \
  --collection-shapes huge-list \
  --methods telepact-binary telepact-packed-binary