Fix master CI: expv zero-input NaN, JET-on-1.12 QA, GPU-in-All

[ChrisRackauckas-Claude]

Fixes three independent failures on the master grouped-tests CI.

1. Core: NaN == 0.0 at basictests.jl:307 (zero-input expv)

The real expv!(w, t::Real, Ks) method was missing the iszero(beta) guard the complex method already has. For a zero input vector firststep! skips initializing the Krylov basis V (it only fills V[:,1] when beta != 0), so the final lmul!(beta, mul!(w, @view(V[:,1:m]), expHe)) computes 0 * <uninitialized memory>, which is NaN whenever V holds garbage — explaining why the failure was flaky (heap-dependent: green on some OS/runs, NaN on others). Added the same early-return guard so expv of a zero vector is exactly zero.

Verified locally: full GROUP=Core Pkg.test passes on Julia 1.10 and 1.12 (it reliably produced NaN on 1.10 before).

2. QA: 6 JET failures on the 1 (= Julia 1.12) channel

lts (1.10) was green; only 1 (1.12) failed. On 1.12 JET traces into LinearAlgebra/Base internals — norm(::Vector) → norm_recursive_check → iterate(::Nothing), and the broadcast unalias/copyto_unaliased! path over Adjoint{T, Union{}} — and reports abstract-interpretation artifacts there that this package does not control. Scoped the QA report_calls to target_modules = (ExponentialUtilities,) (the standard JET-as-package-QA configuration), which keeps full coverage of this package's own code.

That scoping surfaced two genuine may be undefined findings, which are fixed here so the scoped analysis is clean (not silenced):

• si in exponential! (exp_baseexp.jl) — conditionally assigned inside if s > 0, used inside a separate if s > 0; now initialized to 0 unconditionally.
• order / kest in kiops (kiops.jl) — carried across loop iterations via the orderold/kestold "reuse" flags but only conditionally assigned; now seeded with their first-iteration defaults.

Verified locally: QA passes 17/17 on Julia 1.10 and 1.12.

3. Core (windows): "CUDA driver not functional"

On Windows the Core job runs the run_tests "All" aggregate, which pulled in the GPU group, and using CUDA errored on the non-GPU runner. Marked the GPU group in_all = false so it only ever runs under an explicit GROUP=GPU on the self-hosted CUDA runner. Verified locally: GROUP=All now runs only Core/basictests.jl, never GPU/gputests.jl.

Not addressed (reported separately)

• Core (julia pre, macos-latest): Static Arrays tolerance failure at basictests.jl:265 (expv(t,A,b) ≈ exp(t*A)*b). On linux Julia 1.13-rc1 the worst relative error is 1.25e-15; the macOS-pre failure shows ~1e-7. This is a macOS/1.13-rc-specific accuracy difference I could not reproduce or correctly fix on linux, and I will not loosen the tolerance without being able to prove the macOS deviation is benign.
• GPU (self-hosted): requires CUDA hardware (infra), out of scope here.

Please ignore until reviewed by @ChrisRackauckas.