Add JET.jl tests for type stability analysis

[ChrisRackauckas-Claude]

Summary

• Add JET.jl as a test dependency for static analysis
• Create test/jet_test.jl with type stability checks for key functions
• Include JET tests in the Core1 test group

Changes

test/jet_test.jl (new file)

Tests type stability of key hot-path functions using JET.report_opt:

• accept_step! - main stepping function
• setup_next_step! - RSWM algorithm setup
• calculate_step! - noise generation
• WHITE_NOISE_DIST - white noise distribution
• wiener_randn - random number generation (scalar and array variants)

Project.toml

• Add JET to [extras] section as test dependency
• Add JET compat entry (0.8, 0.9)
• Include JET in test targets

test/runtests.jl

• Include jet_test.jl in the Core1 test group

Testing

• JET analysis shows 0 issues for the entire package
• All 6 optimization tests pass
• Tests gracefully skip when JET is not available

Notes

JET.report_package was intentionally avoided in the test suite because it creates a virtualized module context that can interfere with subsequent tests. The JET.report_opt approach provides targeted type stability verification without this side effect.

Verification

using JET
using DiffEqNoiseProcess

# Full package analysis
result = JET.report_package("DiffEqNoiseProcess"; target_modules=(DiffEqNoiseProcess,))
length(JET.get_reports(result))  # Returns 0

cc @ChrisRackauckas

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