fix: choose safe default input stream

[MilesCranmerBot]

Summary

• choose stdin by default only for POSIX TTY sessions where interactive input should be safe
• fall back to devnull by default for Windows, WSL, non-TTY, closed, or unreadable streams
• preserve explicit input_stream=stdin / input_stream=devnull overrides
• add targeted option tests for WSL detection, default selection, and explicit overrides
• remove the ad hoc WSL CI job since the unit tests now cover the policy without a flaky Windows/WSL setup step

Tests

• julia --project=. -e 'using Pkg; Pkg.test(; test_args=["unit/basic"])'

[github-actions]

Benchmark Results (Julia v1)

Time benchmarks

	master	2a347d3...	master / 2a347d3...
search/multithreading	15.2 ± 0.58 s	14.8 ± 0.28 s	1.03 ± 0.044
search/serial	32.1 ± 0.21 s	32.2 ± 0.06 s	0.998 ± 0.0066
utils/best_of_sample	1.86 ± 0.58 μs	1.69 ± 0.37 μs	1.1 ± 0.42
utils/check_constraints_x10	17.2 ± 4.4 μs	17.2 ± 4.4 μs	0.998 ± 0.36
utils/compute_complexity_x10/Float64	2.14 ± 0.09 μs	2.16 ± 0.09 μs	0.991 ± 0.059
utils/compute_complexity_x10/Int64	2.04 ± 0.09 μs	2.08 ± 0.08 μs	0.981 ± 0.057
utils/compute_complexity_x10/nothing	1.55 ± 0.09 μs	1.55 ± 0.09 μs	1 ± 0.082
utils/insert_random_op_x10	5.13 ± 1.6 μs	5.08 ± 1.7 μs	1.01 ± 0.46
utils/next_generation_x100	0.439 ± 0.024 ms	0.443 ± 0.025 ms	0.991 ± 0.079
utils/optimize_constants_x10	0.0332 ± 0.0077 s	0.0333 ± 0.0072 s	0.996 ± 0.32
utils/randomly_rotate_tree_x10	8.29 ± 0.94 μs	8.28 ± 0.94 μs	1 ± 0.16
time_to_load	2.68 ± 0.091 s	2.72 ± 0.0084 s	0.984 ± 0.033

Memory benchmarks

	master	2a347d3...	master / 2a347d3...
search/multithreading	0.204 G allocs: 52.6 GB	0.205 G allocs: 53.5 GB	0.983
search/serial	0.209 G allocs: 56.7 GB	0.209 G allocs: 56.7 GB	1
utils/best_of_sample	0.038 k allocs: 3.25 kB	0.038 k allocs: 3.25 kB	1
utils/check_constraints_x10	0.034 k allocs: 0.875 kB	0.034 k allocs: 0.875 kB	1
utils/compute_complexity_x10/Float64	0 allocs: 0 B	0 allocs: 0 B
utils/compute_complexity_x10/Int64	0 allocs: 0 B	0 allocs: 0 B
utils/compute_complexity_x10/nothing	0 allocs: 0 B	0 allocs: 0 B
utils/insert_random_op_x10	0.041 k allocs: 1.62 kB	0.041 k allocs: 1.62 kB	1
utils/next_generation_x100	4.62 k allocs: 0.275 MB	4.63 k allocs: 0.276 MB	0.998
utils/optimize_constants_x10	24.3 k allocs: 25.1 MB	23.8 k allocs: 24.8 MB	1.01
utils/randomly_rotate_tree_x10	0.042 k allocs: 1.34 kB	0.042 k allocs: 1.34 kB	1
time_to_load	0.145 k allocs: 11 kB	0.145 k allocs: 11 kB	1

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[MilesCranmer]

Not needed anymore due to #623 #562