[not-matthias]

Add --always-sparkplug to the exec-harness node wrapper

The wrapper mirrors getV8Flags(), but its analysis flag set was missing
--always-sparkplug. The integration requires it so the measured code is
compiled eagerly and does not tier up during the run.

This only becomes visible with the integration-side self-restart: a benchmark
process whose execArgv lacks a required flag replaces itself with the missing
ones. Without this flag, every normal codspeed exec analysis run would restart
once, even though the wrapper had already supplied the flags. With the mirror
complete, the restart only fires for launchers that really bypass the wrapper,
such as Bazel's rules_js.

Verified by running the wrapper with Node 24 in analysis mode and comparing its
execArgv with getV8Flags() from @codspeed/core: the sets match, and the
expected_flags table in the wrapper tests matches the emitted order.

Companion change: CodSpeedHQ/codspeed-node#113

Refs COD-4038

[codspeed]

Merging this PR will not alter performance

2 warnings

⚠️ Walltime results may be unreliable

Some benchmarks used the Walltime instrument outside CodSpeed Macro Runners, which can make the results inconsistent.

Learn more about Macro Runners

See affected benchmarks

⚠️ 8 benchmarks are dominated by system calls

System calls cannot be simulated consistently and are left out of the measure. The reported value understates the real cost. Switch to the Walltime instrument to measure them.

Learn more about system calls

See affected benchmarks

✅ 41 untouched benchmarks
⏩ 6 skipped benchmarks¹

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_{Comparing cod-4038-mirror-always-sparkplug (b7d00c0) with main (d14d95d)}

Footnotes

1. 6 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩