CI: CodSpeed: set "mode" to "simulation"

[shenanigansd]

Now required by v4.

[codspeed-hq]

CodSpeed Performance Report

Merging this PR will improve performance by 10.03%

_{Comparing shenanigansd-patch-1 (9f62f8c) with main (ceeb039)¹}

Summary

⚡ 1 improved benchmark
✅ 1 untouched benchmark

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
⚡	test_stutter[0.0-cats are small-cats are small]	119.8 µs	108.9 µs	+10.03%

Footnotes

1. No successful run was found on main (65a975c) during the generation of this report, so ceeb039 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[Copilot]

Pull request overview

This PR updates the CodSpeed workflow configuration to add the required mode: "simulation" parameter for v4 compatibility. The change ensures the benchmark workflow continues to function correctly with CodSpeed action v4.7.0.

Changes:

• Added mode: "simulation" parameter to CodSpeed action configuration in the workflow file

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