fix: Exclude setup time from benchmark in walltime mode

[toby-coleman]

Suggested fix for #113:

• It appears that the issue is limited to walltime mode.
• Small fix to the ordering, plus a test.

Generated with AI Agent (GPT 5.3 Codex in Copilot)

Fix #113

[adriencaccia]

Good catch, it was indeed not intended.

Thanks for the contribution @toby-coleman!

[codspeed-hq]

Merging this PR will degrade performance by 27.07%

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 22 improved benchmarks
❌ 16 regressed benchmarks
✅ 239 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	WallTime	test_sum_of_squares[sum_of_squares_sum_comprehension_product]	193.9 µs	199.1 µs	-2.59%
❌	WallTime	test_multiprocessing_map[10000]	85.2 ms	116.9 ms	-27.07%
❌	WallTime	test_make_lowpass	5.3 µs	6.1 µs	-11.79%
⚡	WallTime	test_sum_squares_slow	361.7 µs	322.3 µs	+12.21%
❌	WallTime	test_tcp_connection[google.com-443]	1.1 ms	1.2 ms	-4.69%
❌	WallTime	test_make_peak	6.4 µs	6.6 µs	-2.27%
❌	WallTime	test_iir_filter_process	3 µs	3.1 µs	-4.11%
❌	WallTime	test_hamilton_cycle[graph0]	25 µs	26.7 µs	-6.17%
❌	WallTime	test_generate_all_combinations[5-4]	10.3 µs	11.5 µs	-10.53%
⚡	WallTime	test_fs_read[1000]	827.6 ns	803.3 ns	+3.03%
⚡	WallTime	test_threadpool_map[10]	2.6 ms	2.5 ms	+2.02%
⚡	WallTime	test_process_creation[cat /dev/null]	5.4 ms	5 ms	+9.15%
❌	WallTime	test_noop_pass	468.2 ns	481.6 ns	-2.79%
⚡	WallTime	test_multiprocessing_map[100]	58.3 ms	56.4 ms	+3.33%
❌	WallTime	test_tcp_connection[8.8.8.8-53]	659.2 µs	680.6 µs	-3.15%
⚡	WallTime	test_make_highshelf	7.7 µs	7.5 µs	+2.33%
❌	WallTime	test_sum_of_squares[sum_of_squares_sum_labmda_product]	274.8 µs	295.8 µs	-7.09%
⚡	WallTime	test_process_creation[echo hello]	2.5 ms	2.1 ms	+14.89%
❌	WallTime	test_array_alloc[100]	1.2 µs	1.2 µs	-5.03%
⚡	WallTime	test_tcp_connection[1.1.1.1-53]	958.8 µs	774.9 µs	+23.73%
...	...	...	...	...	...

ℹ️ Only the first 20 benchmarks are displayed. Go to the app to view all benchmarks.

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_{Comparing toby-coleman:fix/pedantic-walltime-mode (4a1f0f8) with master (aa267f3)}