bug fix - html rendering when multiple percentiles are the same

[sjmonson]

Summary

Fixes a bug when an HTML benchmark reports is generated. The HTML report crashes in the browsers with e.g. Error: xs[2] == xs[3] when rendering distributions with consecutive duplicate percentile values.

This occurs when benchmarks have limited data points (e.g., < 10 requests), causing multiple percentiles to collapse to the same value. The visualization library expects strictly increasing x-values and fails when encountering duplicates.

Root Cause

When a benchmark has very few successful requests (e.g., 3 requests), percentile calculations result in many duplicate values:

# Before fix - causes visualization error
{
  "p001": 15.288,
  "p01": 15.288,   # duplicate
  "p05": 15.288,   # duplicate
  "p10": 15.288,   # duplicate
  "p25": 15.288,   # duplicate
  "p50": 16.413,   # unique
  "p75": 16.413,   # duplicate
  "p90": 17.035,   # unique
  ...
}

# After fix - renders successfully
{
  "p001": 15.288,
  "p50": 16.413,
  "p90": 17.035
}

Details

• Added _filter_duplicate_percentiles() helper function to remove consecutive duplicate percentile values
• Override model_dump() in _TabularDistributionSummary to automatically apply filtering during HTML generation
• Added comprehensive unit tests (8 test cases) covering all edge cases

Test Plan

Unit Tests

uv run pytest tests/unit/benchmark/test_html_output.py -v
# 8/8 tests passing

Related

• Replaces bug fix - html rendering when multiple percentiles are the same  #490

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