Compare selector engines with grouped benchmark charts

[jdalton]

Changes

• Split the charts into six selector categories, with four selectors per SVG.
• Compare NWSAPI 2.0.0, 2.2.27, the unreleased engine at 7fc3cda, and dom-selector 8.3.2 under jsdom 30.0.1.
• Check ordered results against Chromium before timing. Unsupported selectors have no timing bar.
• Record nine timing rounds, raw samples, source hashes, and machine details. Show slower results as well as faster ones.
• Preserve the selector presets, accessor, cache, and memory harnesses under scripts/repo/bench. Use the root pnpm catalog and existing process helpers.
• Replace the old historical reports with current charts and concise benchmark instructions.

Validation

• 24 selectors checked against Chromium 151.0.7922.34; all candidate results agree. NWSAPI 2.0.0 does not support three of the logical selectors.
• Six optimized SVGs generated; representative charts inspected in light and dark mode.
• 578 Node tests passed; existing expected failures and browser skips remain.
• API, SVG, formatting, lint, and type checks passed.
• Diagnostic smoke runs passed for selector presets, accessor costs, cache limits, and memory.

See docs/benchmarks.md for the charts and reproduction commands. These are warm-query measurements on one fixture, not a universal performance ranking.