Publish the suite on two payload sizes: 256 B and 4 KiB

[leo-gan]

Summary

• Experiment 13 showed that SPSC ranking only changes at 256 B and 4 KiB.
• The default matrix and smoke path now use size_256 and size_4096.
• The dashboard filter is payload size, labelled 256 B and 4 KiB.
• event / telemetry / strings stay in the catalog for older experiments; they are not on the published matrix.
• Item count is still [100, 1000]. That is how many items move in one repetition, not a third size.

This branch also contains Experiment 13 (#32). Merging this PR lands both the finding and the matrix change.

Validation

• Tests: analysis 97 passed; python 14 passed (project venv); javascript 3 passed; dashboard 22 passed.
• Benchmarks: full, all five languages. Stems: csharp 2026-09-01-153914, python 2026-09-01-153922, rust 2026-09-01-153934, c 2026-09-01-153943, javascript 2026-09-01-153947.
• Error CSVs: clean (0 error rows).
• Analysis: 124 / 108 / 84 / 64 / 56 stat groups (python / rust / csharp / c / javascript), types size_256 and size_4096 only.
• Dashboard: sync-data.py updated *_latest.json.gz.
• Experiments 01–12 were not re-timed. They use their own run.yaml (message / document) and do not read the default matrix.

How to read

• 256 B is the small-message cell. The queue usually stores a short reference to bytes already in memory, so making the message a little larger does not change who is first.
• 4 KiB is the large-message cell. Some queues copy every byte, so the handoff takes longer and the order can change (Rust).